The Best EMC FAQ on the Net

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I. How to merge two switches with different active zone sets??Brocade Switches:How to merge two switches with different active zone sets."

Merging Two B-series Directors and/or Switches with Different Active Zoning ConfigurationBefore Beginning The following procedure is disruptive to fabric traffic.:--It will require disabling the switch and the removal of the effective zoning configurations at one step. Removing this

configuration will stop the data flow. Since this step in the procedure takes only a few moments to complete, data should resumeas soon as the new configuration is activated.To evaluate the impact on an OS platforms and applications, please refer to the ESN Topology Guide for OS platform timeoutrecommendations as well as the actual configuration files of the servers to identify their current timeout settings.

Supported Director and Switch TypesThe following information on fabric merging applies to the following EMC Director and Switch types:ED-12000BDS-32B2DS-16B2DS-16BDS-8BNOTE: Also applies to similar OEM version of these switch types. See ESM for latest switch firmware qualification prior to

merging non-EMC Directors and/or Switches into an EMC SAN.

Host Requirements:A host computer with a FTP service is required.

Merging

1. Log into the first switch via telnet or WebToolsa. Known as “swo1” for this exampleb. For DS-16Bs, DS-8Bs, and comparable switch models running firmware 2.5.0d and above, default access zoning must be setto “ALLACCESS”NOTE: This is an offline command that wi ll interrupt data flow.1. Issue switchdisable command2. Issue configure command3. Enter “y” when prompted for “Zoning Operation parameters”

4. Enter “1” when prompted for “Default Access”5. Enter “n” for all other parameters6. Issue switchenable command2. Upload the first switch (or one switch of a multi-switch fabric) configuration to a host using FTPa. Use configupload command or use WebToolsb. Name the file “sw01_config.txt”1. All zoning and configuration data for this switch will be located in this file.3. Log into the second switch via telnet or WebToolsa. Known as “sw02” for this exampleb. For DS-16Bs, DS-8Bs, and comparable switch models running firmware 2.5.0d and above, default access zoning must be setto “ALLACCESS”NOTE: This is an offline command that wi ll interrupt data flow.1. Issue switchdisable command2. Issue configure command3. Enter “y” when prompted for “Zoning Operation parameters”

4. Enter “1” when prompted for “Default Access”5. Enter “n” for all other parameters6. Issue switchenable command4. Upload the switch configuration to a host using FTPa. Use configupload command or use WebToolsb. Name the file “sw02_config.txt”1. All zoning and configuration data for this switch will be located in this file.5. Open in a text editor (i.e. Microsoft Word, VI, emacs, etc) for both “sw01_config.txt” and “sw02_config.txt” filesa. The uploaded configuration contains a list of switches in the fabric, list of ISLs, list of ports, name server data, and zoninginformation.b. For the purposes of merging, one need only be concerned with the zoning section of the uploaded configuration, which maybe found at the end of the file. It contains zones, aliases, and defined and effective configurations.

Example sw01_config.txt Zoning Section



[Zoning]cfg.cfg_1:zone_1zone.zone_1:10:00:00:08:00:00:00:01alias.HBA1:10:00:00:08:00:00:00:01enable:cfg_1Example sw02_config.txt Zoning Section[Zoning]cfg.cfg_2:zone_2zone.zone_2:10:00:00:00:09:00:00:02

alias.HBA2:10:00:00:00:09:00:00:02enable:cfg_2

6. Make a copy of “sw01_config.txt” and rename the copy as “configmerge.txt”7. Copy aliases from “sw02_config.txt”a. Highlight and copy the alias data8. Paste aliases from “sw02_config.txt” to “configmerge.txt”a. Paste under existing alias data in “configmerge.txt”9. Copy zones from “sw02_config.txt”a. Highlight and copy the zone data10. Paste zones from “sw02_config.txt” to “configmerge.txt”a. Paste under existing zone data in “configmerge.txt”11. Copy zone names from “cfg.cfg” line of “[Zoning]” section from “sw02_config.txt” to “configmerge.txt”a. Copy zone name(s) to “cfg.cfg” line after existing zones separating each zone with a semicolonb. The last zone name will not be followed by a semicolon

Example Configmerge.txt Zoning Section After Paste from sw02_config.txt[Zoning]cfg.cfg_1:zone_1;zone_2zone.zone_1:10:00:00:08:00:00:00:01zone.zone_2:10:00:00:00:09:00:00:02alias.HBA1:10:00:00:08:00:00:00:01alias.HBA2:10:00:00:00:09:00:00:02enable:cfg_1

NOTE: Areas highlighted in red above illustrate the additions from “sw02_config.txt”12. Save changes to “configmerge.txt”13. Download “configmerge.txt” to sw01a. Use configdownload command or use WebTools1. If using configdownload command, the switch must be manually disabled before downloading commences. Use the

switchdisable command. After completion, the switch must be manually enabled. Use the switchenable command.2. Using WebTools automatically disables and re-enables the switch.b. After downloading, the newly merged configuration is automatically the effective configuration because it is already specified inthe “[Zoning]” section as the enabled configuration.14. Issue cfgsave command on sw01a. Saves the configuration to flash15. Issue cfgshow command to see defined and effective zoning configurationsExample Output of cfgshow Command on sw01 After Configmerge.txt is Downloaded

Defined configuration:cfg: cfg_1 zone_1; zone_2zone: zone_1 10:00:00:08:00:00:00:01zone: zone_2 10:00:00:00:09:00:00:02alias: HBA1 10:00:00:08:00:00:00:01alias: HBA2 10:00:00:00:09:00:00:02Effective configuration:cfg: cfg_1zone: zone_1 Protocol:ALL 10:00:00:08:00:00:00:01zone: zone_2 Protocol:ALL 10:00:00:00:09:00:00:02

16. On sw02, issue the following commands to remove both defined and effective zoning configurationsa. cfgdisableb. cfgclear c. cfgsave17. Issue cfgshow command to see defined and effective zoning configurationsExample Output of “cfgshow” Command on Second Switch After Removing the ConfigurationDefined configuration:no configuration definedEffective configuration:



no configuration in effect18. Connect the switches via a fiber optic cable to the ports chosen to be E_ports.a. sw02 will inherit the zoning data from sw01 when they exchange fabric parameters.NOTE: Be sure to check that both switches have unique Domain IDs. Be sure to check the fabric parameters such as EDTOV,RATOV, Data Field Size, Core Switch PID are identical.19. Issue cfgshow command on second switch to see defined and effective zoning configurations.Example Output of cfgshow Command on sw02 After Fabric Merge

Defined configuration:

cfg: cfg_1 zone_1; zone_2zone: zone_1 10:00:00:08:00:00:00:01zone: zone_2 10:00:00:00:09:00:00:02alias: HBA1 10:00:00:08:00:00:00:01alias: HBA2 10:00:00:00:09:00:00:02Effective configuration:cfg: cfg_1zone: zone_1 Protocol:ALL 10:00:00:08:00:00:00:01zone: zone_2 Protocol:ALL 10:00:00:00:09:00:00:02

NOTE: Zoning configurations on both switches are now identical.20. Issue switchshow and fabricshow commands to verify a successful fabric merge

Hope this info will help you to replace a switch in your enviornment or merge.

Managing a Fibre Channel SANThere are different type of SAN like IP SAN, NAS over SAN etc... We will discuss about Fibre Channel SAN. It gives you more option inorder to manage and minimize downtime means reducing company cost.

In general if you think storage environments, physical interfaces to storage consisted of parallel SCSI channels supporting a smallnumber of SCSI devices. With Fibre Channel, the technology provides a means to implement robust storage area networks that mayconsist of 100’s of devices. Fibre Channel storage area networks yield a capability that supports high bandwidth storage traffic on theorder of 100 MB/s, and enhancements to the Fibre Channel standard will support even higher bandwidth in the near future.

Depending on the implementation, several different components can be used to build a Fibre Channel storage area network. The FibreChannel SAN consists of components such as storage subsystems, storage devices, and server systems that are attached to a FibreChannel network using Fibre Channel adapters. Fibre Channel networks in turn may be composed of many different types of interconnect entities. Examples of interconnect entities are switches, hubs, and bridges.

There are various type of SAN implementation so lets discuss little bit about physical view and logical view of SAN.

The physical view allows the physical components of a SAN to be identified and the associatedphysical topology between them to be understood. Similarly, the logical view allows the relationships and associations between SANentities to be identified and understood.

Physical View

From a physical standpoint, a SAN environment typically consists of four major classes of components. These four classes are:· End-user platforms such as desktops and/or thin clients;· Server systems;· Storage devices and storage subsystems;· Interconnect entities.

Typically, network facilities based on traditional LAN and WAN technology provide connectivity between end-user platforms and server system components. However in some cases, end-user platforms may be attached to the Fibre Channel network and may accessstorage devices directly. Server system components in a SAN environment can exist independently or as a cluster. As processingrequirements continue to increase, computing clusters are becoming more prevalent.

We are using new term cluster. this itself is big topic to cover but we will have brief idea about cluster. A cluster is defined as a group of independent computers managed as a single system for higher availability, easier manageability, and greater scalability. Server systemcomponents areinterconnected using specialized cluster interconnects or open clustering technologies such as the Fibre Channel - Virtual Interfacemapping. Storage subsystems are connected to server systems, to end–user platforms, and to each other using the facilities of a FibreChannel network. The Fibre Channel network is made up of various interconnect entities that may include switches, hubs, and bridges.



Logical View

From a logical perspective, a SAN environment consists of SAN components and resources, as well as their relationships,dependencies and other associations. Relationships, dependencies, and associations between SAN components are not necessarilyconstrained by physical connectivity. For example, a SAN relationship may be established between a client and agroup of storage devices that are not physically co-located. Logical relationships play a key role in the management of SANenvironments. Some key relationships in the SAN environment are identified below:

· Storage subsystems and interconnect entities;· Between storage subsystems;· Server systems and storage subsystems (including adapters);· Server systems and end-user components;· Storage and end-user components;

· Between server systems.

As a specific example, one type of relationship is the concept of a logical entity group. In this case, server system components andstorage components are logically classified as connected components because they are both attached to the Fibre Channel network. Alogical entity group forms a private virtual network or zone within the SAN environment with a specific set of connected entities as members. Communication within each zone is restricted to its members.In another example, where a Fibre Channel network is implemented using a switched fabric, the Fibre Channel network may further stilbe broken down into logically independent sections called sub-fabrics for each possible combination of data rate and class of service.Sub-fabrics are again divided into regions and extended-regions based on compatible service parameters.Regions and extended regions can also be divided into partitions called zones for administrative purposes.

Host HBA installation and configurationTo display what HBA's are installed.

#prtdiag -v#dmesg#cat /var/adm/messages grep -i wwn more

To set the configuration you must carry out the following:

-changes to the /etc/system file-HBA driver modifications-Persistent binding (HBA and SD driver config file)-EMC recommended changes-Install the Sun StorEdge SAN Foundation package



Changes to /etc/system: ( Plz ignore 3 equal sign when u edit the file)

SCSI throttle === set sd:sd_max_throttle=20Enable wide SCSI === set scsi_options=0x7F8SCSI I/O timeout value === sd:sd_io_time=0x3c (with powerpath)sd:sd_io_time=0x78 (without powerpath

Changes to HBA driver (/kernel/drv/lpfc.conf):

fcp-bind-WWNN=16automap=2fcp-on=1lun-queue-depth=20tgt-queue-depth=512no-device-delay=1 (without PP/DMP) 0 (with PP/DMP)xmt-que-size=256scan-down=0linkdown-tmo=0 (without PP/DMP) 60 (with PP/DMP)

Persistent BindingBoth the lpfc.conf and sd.conf files need to be updated. General format isname="sd" parent="lpfc" target="X" lun="Y" hba="lpfcZ"X is the target number that corresponds to the fcp_bindWWNID lpfcZtXY is the LUN number that corresponds to symmetrix volume

mapping on the symmetrix port WWN or HLU on the clariionZ is the lpfc drive instance number that corresponds to the fcp_bind_WWIDlpfcZtX

To discover the SAN devices#disk;devlinks;devalias (solaris 2.6)#devfsadm (solaris 2.8)#/usr/sbin/update_drv -f sd (solaris 2.9 >)

WindowsTo display what HBA's are installed. use admin tool "device manager"To set the configuration you must carry out the following:#Registry edits#EMC recommended changes#Install emulex exlcfg utility

Arbitrated loop without powerpath/ATF:-

InitLinkFlags=0x00000000 (arbitrated loop, auto-link speed)WaitReady=45LinkDown=45TranslateQueueFull=1

Arbitrated loop with powerpath/ATF:

InitLinkFlags=0x00000000 (arbitrated loop, auto-link speed)WaitReady=10LinkDown=10

Fabric without powerpath/ATF:

InitLinkFlags=0x00000002 (fabric, auto-link speedWaitReady=45LinkDown=45TranslateQueueFull=1

Fabric with powerpath/ATF:

InitLinkFlags=0x00000002 (fabric, auto-link speed)WaitReady=10LinkDown=10

Modifying the EMC environment :In the shortcut for the elxcfg add the "--emc" option to the target option.



To discover the SAN devicescontrol panel -> admin tools -> computer management -> select disk management -> (top menu)action -> rescan tools

HP

To display what HBA's are installed.

#/opt/fcms/bin/fcmsutil /dev/td# (A5158A HBA)#/opt/fc/bin/fcutil /dev/fcs# (A6685A HBA)

On a HP system there is no additional software to install. The HP systems Volume address setting must be enabledon the SAN, youcan check this will the following command.

#symcfg -sid -FA all list (confirm that the volume set addressing is set to yes)

To discover the SAN devices:#ioscan -fnC disk (scans hardware busses for devices according to class)#insf -e (install special device files)

AIX

To display what HBA's are installed#lscfg#lscfg -v -l fcs*

To set the configuration you must carry out the following:#List HBA WWN and entry on system#Determine code level of OS and HBA#Download and install EMC ODM support fileset

#run /usr/lpp/Symmetrix/bin/emc_cfgmgr (symmetrix) #or /usr/lpp/emc/CLARiiON/bin/emc_cfgmgr (clariion)

To discover the SAN devices#/usr/lpp/EMC/Symmetrix/bin/emc_cfgmgr -vif the above does not work reboot server

Hope this will be documented and useful info for novice user.

Handling BCV and Clone Disk on Veritas Volume Manager.

Handling BCV and Clone Disk on Veritas Volume Manager.

Get Output of Vxdisk List command

# vxdisk list

Vxdisk list command showing that some disks are marked with the udid_mismatch flag.

Write a New UUID to Disk

You can use the following command to update the unique disk identifier (UDID) for one or more disks:

# vxdisk [-f] [-g diskgroup] updateudid disk ...

Note : The -f option must be specified if VxVM has not raised the udid_mismatch flag for a disk.

Importing a disk group containing cloned/BCV disks

You can then import the cloned disks by specifying the -ouseclonedev=on option to the vxdgimport command, as shown in thisexample:

# vxdg -o useclonedev=on [-o updateid] import mydg ( Group Name )

Note: This form of the command allows only cloned disks to be imported. All non-cloned disks remain unimported. .) However, the



import fails if multiple copies of one or more cloned disks exist.

You can use the following command to tag all the disks in the disk group that are to be imported:

# vxdisk [-g diskgroup] settag tagname disk ...

where tagname is a string of up to 128 characters, not including spaces or tabs.For example, the following command sets the tag, my_tagged_disks, on several disks that are to be imported together:

You can use the following command to ensure that a copy of the metadata is placed on a disk, regardless of the placement policy for the disk group:

# vxdisk [-g diskgroup] set disk keepmeta=always

Alternatively, use the following command to place a copy of the configurationdatabase and kernel log on all disks in a disk group that share a given tag:

# vxdg [-g diskgroup] set tagmeta=on tag=tagname nconfig=all nlog=all

To check which disks in a disk group contain copies of this configuration information, use the vxdglistmeta command:

# vxdg [-q] listmeta diskgroup

The tagged disks in the disk group may be imported by specifying the tag to the vxdgimport command in addition to the

-ouseclonedev=on option:

# vxdg -o useclonedev=on -o tag=my_tagged_disks import mydg

If you have already imported the non-cloned disks in a disk group, you can usethe -n and -t option to specify a temporary name for the disk group containingthe cloned disks:

# vxdg -t -n clonedg -o useclonedev=on -o tag=my_tagged_disks import mydg

iSCSI details

I tried to collect some good information on iSCSI driver details which was request by some reader. Hope this will help you on iSCSI

queries. Leave comment if it is useful... I will try to write iSCSI overview in next entry. Happy Reading!!!!!!

The iSCSI driver provides a transport for SCSI requests and responses to storage devices via an IP network instead of using a directattached SCSI bus channel or an FC connection. The SN 5400 Series Storage Router, in turn, transports these SCSI requests andresponses received via the IP network between it and the storage devices attached to it. Once the iSCSI driver is installed, the host willproceed with a discovery process for storage devices as follows:1. The iSCSI driver requests available targets through the SendTargets discovery mechanism as configured in the /etc/iscsi.conf configuration file.2. Each iSCSI target sends available iSCSI target names to the iSCSI driver.3. The iSCSI driver discovery daemon process looks up each discovered target

in the /etc/iscsi.bindings file. If an entry exists in the file for the target, the corresponding SCSI target ID is assigned to the target. If noentry exists for the target, the smallest available SCSI target ID is assigned and an entry is written to the /etc/iscsi.bindings file. Thedriver then sends a login request to the iSCSI target.4. The iSCSI target accepts the login and sends target identifiers.5. The iSCSI driver queries the targets for device information.6. The targets respond with the device information.7. The iSCSI driver creates a table of available target devices.Once the table is completed, the iSCSI targets are available for use by thehost using all the same commands and utilities as a direct attached (e.g., viaa SCSI bus) storage device.

- All Linux kernels released on or before Feb 4, 2002 have a known bug in the buffer and page cache design. When any writes to abuffered block device fail, it is possible for the unwritten data to be discarded from the caches, even though the data was never writtento disk. Any future reads will get the prior contents of the disk, and it is possible for applications to get no errors reported.This occurs because block I/O write failures from the buffer cache simply mark the buffer invalid when the write fails. This leaves thebuffer marked clean and invalid, and it may be



discarded from the cache at any time. Any future read either finds no existing buffer or finds the invalid buffer, so the read will fetch olddata from disk and place it in the cache. If the fsync(2) function initiated the write, an error may be returned. If memory pressure on thecache initiated the write, the unwritten buffer may be discarded before fsync(2) is ever called, and in that case fsync will be unaware of the data loss, and will incorrectly report success. There is currently no reliable way for an application to ensure that data written tobuffered block devices has actually been written to disk. Buffered data may be lost whenever a bufferedblock I/O device fails a write. The iSCSI driver attempts to avoid this problem by retrying diskcommands for many types of failures. The MinDiskCommandTimeout defaults to "infinite", which disables the command timeout,allowing commands to be retried forever if the storage device is unreachable or unresponsive.

- All Linux kernels up to and including 2.4.20 have a bug in the SCSI device initialization code. If kernel memory is low, the initializationcode can fail to allocate command blocks needed for proper operation, but will do nothing to prevent I/O from being queued to the non-functional device. If a process queues an I/O request to a SCSI device that has no command blocks allocated, that process will blockforever in the kernel, never exiting and ignoring all signals sent to it while blocked. If the LUN probes initiated by the iSCSI driver areblocked forever by this problem, it will not be possible to stop or unload the iSCSI driver, since the driver code will stillbe in use. In addition, any other LUN probes initiated by the iSCSI driver will also block, since any other probes will lock waiting for theprobe currently in progress to finish. When the failure to allocate command blocks occurs, the kernel will log a message similar to thefollowing:***************************************************************kernel: scsi_build_commandblocks: want=12, space for=0 blocksIn some cases, the following message will also be logged:kernel: scan_scsis: DANGER, no command blocks***************************************************************- Linux kernels 2.2.16 through 2.2.20 and 2.4.0 through 2.4.18 are known to have a problem in the SCSI error recovery process. Insome cases, a successful device reset may be ignored and the SCSI layer will continue on to the later stages of the error recovery

process. The problem occurs when multiple SCSI commands for a particular device are queued in the low-level SCSI driver when adevice reset occurs. Even if the low-level driver correctly reports that all the commands for the device have been completed by thereset, Linux will assume only one command has been completed and continue the error recovery process. (If only one command hastimed out or failed, Linux will correctly terminate the error recovery process followingthe device reset.) This action is undesirable because the later stages of error recovery may send other types of resets, which can affectother SCSI initiators using the same target or other targets on the same bus. It is also undesirable because there are more seriousbugs in the later stages of the Linux SCSI error recovery process. The Linux iSCSI driver now attempts to avoid this problem byreplacing the usual error recovery handler for SCSI commands that timeout or fail.- Linux kernels 2.2.16 through 2.2.20 and 2.4.0 through 2.4.2 may take SCSI devices offline after Linux issues a reset as part of theerror recovery process. Taking a device offline causes all I/O to the device to fail until the HBA driver is reloaded. After the error recovery process does a reset, it sends a SCSI Test Unit Ready command to check if the SCSI target is operationalagain. If this command returns SCSI sense data, instead of correctly retrying the command, Linux will treat it as a fatal error, andimmediately take the SCSI device offline.

The Test Unit Ready will almost always be returned with sense data because most targets return a deferred error in the sense data of the first command received after a reset. This is a way of telling the initiator that a reset has occurred. Therefore, the affected Linuxkernel versions almost always take a SCSI device offline after a reset occurs.This bug is fixed in Linux kernels 2.4.3 and later. The Linux iSCSI driver now attempts to avoid this problem by replacing the usual errorrecovery handler for SCSI commands that timeout or fail.- Linux kernels 2.2.16 through 2.2.21 and 2.4.0 through 2.4.20 appear to have problems when SCSI commands to disk devices arecompleted with a check condition/unit attention containing deferred sense data. This can result in applications receiving I/O errors, shortreads or short writes. The Linux SCSI code may deal with the error by giving up reading or writing the first buffer head of a command,and retrying the remainder of the I/O.The Linux iSCSI driver attempts to avoid this problem by translating deferred sense data to current sense data for commands sent todisk devices.- Linux kernels 2.2.16 through 2.2.21 and 2.4.0 through 2.4.20 may crash on a NULL pointer if a SCSI device is taken offline while oneof the Linux kernel's I/O daemons (e.g. kpiod, kflushd, etc.) is trying to do I/O to the SCSI device. The exact cause of this problem is stilbeing investigated.Note that some of the other bugs in the Linux kernel's error recovery handling may result in a SCSI device being taken offline, thus

triggering this bug and resulting in a Linux kernel crash.- Linux kernels 2.2.16 through 2.2.21 running on uniprocessors may hang if a SCSI disk device node is opened while the Linux SCSIdevice structure for that node is still being initialized.This occurs because the sd driver which controls SCSI disks will loop forever waiting for a device busy flag to be cleared at a certainpoint in the open routine for the disk device. Since this particular loop will never yield control of the processor, the process initializing theSCSI disk device is not allowed to run, and the initialization process can never clear the device busy flag which the sd driver isconstantly checking.A similar problem exists in the SCSI generic driver in some 2.4 kernel versions. The sg driver may crash on a bad pointer if a /dev/sg*device is opened while it is beinginitialized.- Linux kernels prior to 2.4.20-8 (Redhat 9 distribution) had a problem of a rare occurrence of data corruption. This data can be buffer cache data as well as raw I/O data. This problem occurs when iSCSI driver sends the I/O request down to TCP. Linux iSCSI driver handles this problem by copying the incoming I/O buffer temporarily in an internal buffer and then sending the copied data down to TCP



This way the iSCSI driver keeps the original data intact. In case, this sent data gets corrupted (this gets detected by turning on CRC),the driver repeats the foregoing process.The iSCSI Driver Version 3.2.1 for Linux is compatible with SN 5400 Series Storage Routers running software version 3.x or greater. Itis not compatible with SN 5400 Series Storage Routers running software versions 1.x or 2.x.===============================================================================CONFIGURING AND USING THE DRIVER===============================================================================This section describes a number of topics related to conf iguring and using the iSCSI Driver for Linux. The topics covered include:Starting and Stopping the iSCSI driver

Rebooting LinuxDevice NamesAuto-Mounting FilesystemsLog MessagesDynamic Driver ReconfigurationTarget Portal Failover iSCSI HBA StatusUsing Multipath I/O SoftwareMaking Storage Configuration ChangesTarget and LUN Discovery LimitsDynamic Target And LUN DiscoveryPersistent Target BindingTarget AuthenticationEditing The iscsi.conf FileiSCSI Commands and Utilities

Driver File Listing--------------------------------------STARTING AND STOPPING THE iSCSI DRIVER--------------------------------------To manually start the iSCSI driver enter:/etc/init.d/iscsi startThe iSCSI initialization will report information on each detecteddevice to the console or in dmesg(8) output. For example:

********************************************************************Vendor: SEAGATE Model: ST39103FC Rev: 0002Type: Direct-Access ANSI SCSI revision: 02Detected scsi disk sda at scsi0, channel 0, id 0, lun 0SCSI device sda: hdwr sector= 512 bytes.Sectors= 17783240 [8683 MB] [8.7 GB]

sda: sda1********************************************************************The directory /proc/scsi/iscsi will contain a file (the controller number) that contains information about the iSCSI devices.

To see the iscsi devices currently available on this system, use the utility:/usr/local/sbin/iscsi-ls -lIf there are problems loading the iSCSI kernel module, diagnostic information will be placed in /var/log/iscsi.log.To manually stop the iSCSI driver enter:/etc/init.d/iscsi stopWhen the driver is stopped, the init.d script will attempt to kill all processes using iSCSI devices by first sending them "SIGTERM" andthen by sending any remaining processes "SIGKILL". The init.d script will then unmount all iSCSI devices in /etc/fstab.iscsi and kill theiSCSI daemon terminating all connections to iSCSI devices. It is important to note that the init.d script may not be able to successfullyunmount filesystems if they are in use by processes that can't be killed. It is recommended that the you manually stop all applicationsusing the filesystem on iSCSI devices before stopping the driver. Filesystems not listed in /etc/fstab.iscsi will not be unmounted by thescript and should be manually unmounted prior to a system shutdown.It is very important to unmount all filesystems on iSCSI devices before stopping the iSCSI driver. If the iSCSI driver is stopped whileiSCSI devices are mounted, buffered writes may not be committed to disk and file system corruption may occur.---------------REBOOTING LINUX---------------The Linux "reboot" command should not be used to reboot the system while iSCSI devices are mounted or being used since the"reboot" command will not execute the iSCSI shutdown script in /etc/rc6.d/ and file system corruption may occur. To safely reboot aLinux system, enter thefollowing command:/sbin/shutdown -r nowAll iSCSI devices should be unmounted prior to a system shutdown or reboot.



• ------------

DEVICE NAMES------------Because Linux assigns SCSI device nodes dynamically whenever a SCSI logical unit is detected, the mapping from devicenodes (e.g., /dev/sda or /dev/sdb) to iSCSI targets and logical units may vary.Variations in process scheduling and network delay may result in iSCSI targets being mapped to different SCSI device nodesevery time the driver is started. Because of this variability, configuring applications or operating system utilities to use thestandard SCSI device nodes to access iSCSI devices may result in SCSI commands being sent to the wrong target or logicalunit.

To provide a more reliable namespace, the iSCSI driver scans the system to determine the mapping from SCSI device nodesto iSCSI targets, and then creates a tree of directories and symbolic links under /dev/iscsi to make it easier to use a particular iSCSI target's logical units.Under /dev/iscsi, there will be a directory tree containing subdirectories for each iSCSI bus number, each target id number onthe bus, and each logical unit number for each target. For example, the whole disk device for bus 0, target id 0, LUN 0 would be /dev/iscsi/bus0/target0/lun0/disk.In each logical unit directory there will be a symbolic link for each SCSI device node that may be connected to that particular logical unit. These symbolic links are modeled after the Linuxdevfs naming convention.The symbolic link 'disk' will map to the whole-disk SCSI device node(e.g., /dev/sda, /dev/sdb, etc.).The symbolic links 'part1' through 'part15' will map to eachpartition of that SCSI disk (e.g., /dev/sda1, dev/sda15, etc.).Note that these links will exist regardless of the number of disk partitions. Opening the partition devices will result in an error if the partition does not actually exist on the disk.The symbolic link 'mt' will map to the auto-rewind SCSI tape device node for this LUN (e.g., /dev/st0), if any. Additional links for'mtl', 'mtm', and 'mta' will map to the other auto-rewind devices (e.g., /dev/st0l, /dev/st0m, /dev/st0a), regardless of whether thesedevice nodes actually exist or could be opened. The symbolic link 'mtn' will map to the no-rewind SCSI tape device node for this LUN (e.g., /dev/nst0), if any. Additional links for 'mtln', 'mtmn', and 'mtan' will map to the other no-rewind devices (e.g.,/dev/nst0l, /dev/nst0m, /dev/nst0a), regardless of whether those device nodes actually exist or could be opened. The symboliclink 'cd' will map to the SCSI cdrom device node for this LUN (e.g., /dev/scd0), if any.The symbolic link 'generic' will map to the SCSI generic devicenode for this LUN (e.g., /dev/sg0), if any.Because the symlink creation process must open all of the SCSIdevice nodes in /dev in order to determine which nodes map toiSCSI devices, you may see many modprobe messages logged to syslogindicating that modprobe could not find a driver for a particular combination of major and minor numbers. This is harmless, and can

be ignored. The messages occur when Linux is unable to find adriver to associate with a SCSI device node that the iSCSI daemonis opening as part of it's symlink creation process. To preventthese messages, the SCSI device nodes with no associated high-levelSCSI driver can be removed.-------------------------AUTO-MOUNTING FILESYSTEMS-------------------------Filesystems installed on iSCSI devices cannot be automatically mounted atsystem reboot due to the fact that the IP network is not yet configured atmount time. However, the driver provides a method to auto-mount thesefilesystems as soon as the iSCSI devices become available (i.e., after the IPnetwork is configured).To auto-mount a filesystem installed on an iSCSI device, follow these steps:1. List the iSCSI partitions to be automatically mounted in

/etc/fstab.iscsi which has the same format as /etc/fstab. The/etc/fstab.iscsi file will not be overwritten when the driver isinstalled nor will removing the current version of the driver delete/etc/fstab.iscsi. It is left untouched during an install.2. For each filesystem on each iscsi device(s), enter the logical volume onwhich the filesystem resides. The mount points must exist for thefilesystems to be mounted. For example, the following /etc/fstab.iscsientries will mount the two iSCSI devices specified (sda and sdb):*************************************************************************#device mount FS mount backup fsck#to mount point type options frequency pass/dev/sda /mnt/t0 ext2 defaults 0 0/dev/sdb /mnt/t1 ext2 defaults 0 0*************************************************************************



3. Upon a system restart, the iSCSI startup script invokes theiscsi-mountall script will try to mount iSCSI devices listed in/etc/fstab.iscsi file. iscsi-mountall tries to mount the iSCSI devicesfor "NUM_RETRIES" (default value 10) number of times, at an interval of "SLEEP_INTERVAL" seconds (default value 1) between each attempt, givingthe driver the time to establish a connection with an iSCSI target.The value of these parameters can be changed in the iscsi-mountall scriptif the devices are not getting configured in the system within thedefault time periods.

Due to variable network delays, targets may not always become available in thesame order from one boot to the next. Thus, the order in which iSCSI devicesare mounted may vary and may not match the order the devices are listed in/etc/fstab.iscsi You should not assume mounts of iSCSI devices will occur inany particular order.Because of the variability of the mapping between SCSI device nodesand iSCSI targets, instead of directly mounting SCSI device nodes,it is recommended to either mount the /dev/iscsi tree symlinks,mount filesystem UUIDs or labels (see man pages for mke2fs, mount,and fstab), or use logical volume management (see Linux LVM) toavoid mounting the wrong device due to device name changes resultingfrom iSCSI target configuration changes or network delays.------------LOG MESSAGES------------

The iSCSI driver contains components in the kernel and user level.The log messages from these components are sent to syslog. Based on thesyslogd configuration on the Linux host, the messages will be sent to theappropriate destination. For example, if /etc/syslog.conf has the followingentry:

*.info /var/log/messagesthen all log messages of level 'info' or higher will be sent to/var/log/messages.

If /etc/syslog.conf has the following entry:*.info;kern.none /var/log/messagesthen all log messages (except kernel messages) of level info or higher will be sent to /var/log/messages.If /etc/syslog.conf has the following entry:

kern.* /dev/consolethen all kernel messages will be sent to the console.All messages from the iSCSI driver when loading the iSCSI kernelmodule will be placed in /var/log/iscsi.log.The user can also use dmesg(8) to view the log messages.------------------------------DYNAMIC DRIVER RECONFIGURATION------------------------------Configuration changes can be made to the iSCSI driver without having to stopit or reboot the host system. To dynamically change the configuration of thedriver, follow the steps below:1. Edit /etc/iscsi.conf with the desired configuration changes.2. Enter the following command:/etc/init.d/iscsi reloadThis will cause the iSCSI daemon to re-read /etc/iscsi.conf file and tocreate any new DiscoveryAddress connections it finds. Those discoverysessions will then discover targets and create new target connections.Note that any configuration changes will not affect existing target sessions.For example, removal of a DiscoveryAddress entry from /etc/iscsi.conf will not cause the removal of sessions to targets discovered through thisDiscoveryAddress, but it will cause the removal of the discovery sessioncorresponding to the deleted DiscoveryAddress.----------------------TARGET PORTAL FAILOVER----------------------Some SN 5400 Series Storage Routers have multiple Gigabit Ethernet ports.Those systems may be configured to allow iSCSI target access via multiplepaths. When the iSCSI driver discovers targets through a multi-port SN 5400Series system, it also discovers all the IP addresses that can be used to



reach each of those targets.When an existing target connection fails, the iSCSI driver will attempt toconnect to that target using the next available IP address. You can alsochoose a preferred portal to which the iSCSI driver should attempt to connectto when the iSCSI driver is started or whenever automatic portal failover occurs. This is significant in a situation when you want the connectionto the targets to be made through a faster network portal (for example, whenthe I/Os are going through a Gigabit Ethernet interface and you do notprefer the connection to failover to a slower network interface).

The preference for portal failover can be specified through the"PreferredPortal" or "PreferredSubnet" parameter in /etc/iscsi.conf.If this preference is set, then on any subsequent failover the driver willfirst try to failover to the preferred portal or preferred subnet whichever is specified in the conf file. If both preferred portal and preferred subnetentries are present in the conf file then the preferred portal takesprecedence. If the preferred portal or preferred subnet is unreachable,then the driver will continuously rotate through the list of availableportals until it finds one that is active.The Portal Failover feature is turned on by default and the whole process of failover occurs automatically. You can chose to turn off portal failover by disabling the portal failover parameter in /etc/iscsi.conf.If a target advertises more than one network portal, you can manuallyswitch portals by writing to the HBA's special file in /proc/scsi/iscsi/.For example, if a target advertises two network portals:

10.77.13.248:3260 and 192.168.250.248:3260.If the device is configured with targetId as 0, busId as 0, HBA's hostnumber is 3 and you want to switch the target from10.77.13.248 to 192.169.250.248, use the following command:echo "target 0 0 address 192.168.250.248" > /proc/scsi/iscsi/3Where the syntax is:echo "target address " >/proc/scsi/iscsi/The host system must have multiple network interfaces to effectivelyutilize this failover feature.----------------iSCSI HBA STATUS----------------The directory /proc/scsi/iscsi will contain a special file that can beused to get status from your iSCSI HBA. The name of the file will

be the iSCSI HBA's host number, which is assigned to the driver by Linux.

When the file is read, it will show the driver's version number,followed by a list all iSCSI targets and LUNs the driver has foundand can use.Each line will show the iSCSI bus number, target id number, andlogical unit number, as well as the IP address, TCP port, andiSCSI TargetName. If an iSCSI session exists, but no LUNs haveyet been found for a target, the LUN number field will contain aquestion mark. If a TCP connection is not currently established,the IP address and port number will both appear as question marks.----------------------------USING MULTIPATH I/O SOFTWARE----------------------------If a third-party multipath I/O software application is being used inconjunction with the iSCSI driver (e.g., HP Secure Path), it may benecessary to modify the configuration of the driver to allow themulti-pathing software to operate more efficiently. If you are usinga multipath I/O application, you may need to set the "ConnFailTimeout"parameter of the iSCSI driver to a smaller value so that SCSI commandswill fail more quickly when an iSCSI network connection drops allowingthe multipath application to try a different path to for access to thestorage device. Also, you may need to set the "MaxDiskCommandTimeout"to a smaller value (e.g., 5 or 10 seconds), so that SCSI commands tounreachable or unresponsive devices will fail more quickly and themultipath software will know to try a different path to the storage device.Multipath support in the iSCSI driver can be turned on by settingMultipath=<"yes" or "portal" or "portalgroup"> in /etc/iscsi.conf.



If Multipath=<"yes" or "portal">, then the discovered targets thatare configured to allow access via multiple paths will have a separateiSCSI session created for each path (i.e., iSCSI portal). The targetportal failover feature should not be used if Multipath=<"yes" or "portal">since multiple sessions will be established with all available paths.------------------------------------MAKING STORAGE CONFIGURATION CHANGES------------------------------------Making changes to your storage configuration, including adding or

removing targets or LUNs, remapping targets, or modifying targetaccess, may change how the devices are presented to the host operatingsystem. This may require corresponding changes in the iSCSI driver configuration and /etc/vfstab file.It is important to understand the ramifications of SCSI routingservice configuration changes on the hosts accessing the associatedstorage devices. For example, changing the instance configurationmay change the device presentation to the host's iSCSI driver,effectively changing the name or number assigned to the deviceby the host operating system. Certain configuration changes,such as adding or deleting targets, adding or deleting LUNswithin a particular target, or adding or deleting entire instancesmay change the order of the devices presented to the host.Even if the host is only associated with one SCSI routingservice instance, the device order could make a difference.

Typically, the host operating system assigns drive identificationsin the order they are received based on certain criteria. Changingthe order of the storage device discovery may result in a changeddrive identification. Applications running on the host may requiremodifications to appropriately access the current drives.If an entire SCSI routing service instance is removed, or thereare no targets available for the host, the host's iSCSI driver configuration file must be updated to remove the appropriatereference before restarting the iSCSI driver. If a host's iSCSIconfiguration file contains an IP address of a SCSI routingservice instance that does not exist, or has no targets availablefor the host, the iSCSI driver will not complete a login andwill keep on trying to discover targets associated with this SCSIrouting service instance.In general, the following steps are normally required when reconfiguring

iSCSI storage:1. Unmount any filesystems and stop any applications using iSCSIdevices.2. Stop the iSCSI driver by entering:/etc/init.d/iscsi stop3. Make the appropriate changes to the iSCSI driver configuration file. Remove any references to iSCSIDiscoveryAddresses that have been removed, or thatno longer have valid targets for this host.4. Modify /etc/fstab.iscsi and application configurations asappropriate.5. Restart the iSCSI driver by entering:/etc/init.d/iscsi startFailure to appropriately update the iSCSI configuration usingthe above procedure may result in a situation that preventsthe host from accessing iSCSI storage resources.-------------------------------TARGET AND LUN DISCOVERY LIMITS-------------------------------The bus ID and target ID are assigned by the iSCSI initiator driver whereas the lun ID is assigned by the iSCSI target. The driver providesaccess to a maximum of 256 bus IDs with each bus supporting 256 targetsand each target capable of supporting 256 LUNs. Any discovered iSCSIdevice will be allocated the next available target ID on bus 0.If a target ID > 256 on bus 0, then a next available target ID on bus 1will be allocated. If a bus ID > 256 and LUN ID > 256 it will be ignoredby the driver and will not be configured in the system.--------------------------------DYNAMIC TARGET AND LUN DISCOVERY



--------------------------------When using iSCSI targets that support long-lived iSCSI discovery sessions,such as the Cisco 5400 Series, the driver will keep a discovery sessionopen waiting for change notifications from the target. When a notificationis received, the driver will rediscover targets, add any new targets, andactivate LUNs on all targets.If a new LUN is dynamically added to an existing target on a SCSI routinginstance with which the driver has established a connection, then the driver does not automatically activate the new LUN. The user can manually activate

the new LUN by executing the following command:echo "scsi add-single-device " >/proc/scsi/scsiwhere;HBA#: is the controller number present under /proc/scsi/iscsi/bus-id: is the bus number present on controller .target-id: is the target ID present on ,.LUN: new LUN added dynamically to the target.

-------------------------PERSISTENT TARGET BINDING-------------------------This feature ensures that the same iSCSI bus and target id number are usedfor every iSCSI session to a particular iSCSI TargetName, and a Linux SCSItarget always maps to the same physical storage device from one reboot to

the next.This feature ensures that the SCSI numbers in the device symlinks describedabove will always map to the same iSCSI target.Note that because of the way Linux dynamically allocates SCSI device nodesas SCSI devices are found, the driver does not and cannot ensure that anyparticular SCSI device node (e.g., /dev/sda) will always map to the sameiSCSI TargetName. The symlinks described in the section on Device Names areintended to provide a persistent device mapping for use by applications andfstab files, and should be used instead of direct references to particular SCSI device nodes.The file /etc/iscsi.bindings is used by the iSCSI daemon to store bindings of iSCSI target names to SCSI target ID's. If the file doesn't exist,it will be created when the driver is started. If an entry exists for adiscovered target, the Linux target ID from the entry is assigned to thetarget. If no entry exists for a discovered target, an entry is written to

the file. Each line of the file contains the following fields:BusId TargetId TargetNameAn example file would be:*****************************************************************************0 0 iqn.1987-05.com.cisco.00.7e9d6f942e45736be69cb65c4c22e54c.disk_one0 1 iqn.1987-05.com.cisco.00.4d678bd82965df7765c788f3199ac15f.disk_two0 2 iqn.1987-05.com.cisco.00.789ac4483ac9114bc6583b1c8a332d1e.disk_three*****************************************************************************Note that the /etc/iscsi.bindings file will permanently contain entriesfor all iSCSI targets ever logged into from this host. If a target isno longer available to a host you can manually edit the file and removeentries so the obsolete target no longer consumes a SCSI target ID.If you know the iSCSI target name of a target in advance, and you wantit to be assigned a particular SCSI target ID, you can add an entrymanually. You should stop the iSCSI driver before editing the/etc/iscsi.bindings file. Be careful to keep an entire entry on a singleline, with only whitespace characters between the three fields. Do notuse a target ID number that already exists in the file.*****************************************************************************NOTE: iSCSI driver versions prior to 3.2 used the file /var/iscsi/bindingsinstead of /etc/iscsi.bindings. The first time you start the new driver version, it will change the location and the name of the bindings fileto /etc/iscsi.bindings*****************************************************************************---------------------TARGET AUTHENTICATION---------------------The CHAP authentication mechanism provides for two way authentication betweenthe target and the initiator. The authentication feature on the SN 5400



system has to be enabled to make use of this feature. The username andpassword for both initiator side and target side authentication needs to belisted in /etc/iscsi.conf. The username and password can be specified asglobal values or can be made specific to the target address. Please refer tothe Editing The iscsi.conf File section of this document for a more detaileddescription of these parameters.---------------------------EDITING THE ISCSI.CONF FILE---------------------------

The /etc/iscsi.conf file is used to control the operation of the iSCSI driver by allowing the user to configure the values for anumber of programmable parameters. These parameters can be setup to apply to specific configuration types or they can besetup to apply globally. The configuration types that are supported are:

• DiscoveryAddress = SCSI routing instance IP address with format a.d.c.d or a.b.c.d:n or hostname.

• TargetName = Target name in 'iqn' or 'eui' format eg: TargetName = iqn.1987-05.com.cisco:00.0d1d898e8d66.t0

• TargetIPAddress = Target name with format a.b.c.d/n

• Subnet = Network portal IP address with format a.b.c.d/n or a.b.c.d&hex

• Address = Network portal IP address with format a.b.c.d/32

The complete list of parameters that can be applied either globally or to the configuration types listed above are shown below.Not all parameters are applicable to all configuration types.

• Username = CHAP username used for initiator authentication by the target.

• OutgoingUsername = <>

• Password = CHAP password used for initiator authentication by the target.

• OutgoingPassword = <>

• IncomingUsername = CHAP username for target authentication by the initiator.

• IncomingPassword = CHAP password for target authentication by the initiator.

• HeaderDigest = Type of header digest support the initiator is requesting of the target.

• DataDigest = Type of data digest support the initiator is requesting of the target.

• PortalFailover = Enabling/disabling of target portal failover feature.

• PreferredSubnet = IP address of the subnet that should be used for a portal failover.

• PreferredPortal = IP address of the portal that should be used for a portal failover.

• Multipath = Enabling/disabling of multipathing feature.

• LoginTimeout = Time interval to wait for a response to a login request to be received from a target before failing a connection

attempt.• AuthTimeout = Time interval to wait for a response to a login request containing authentication information to be received from

a target before failing a connection attempt.

• IdleTimeout = Time interval to wait on a connection with no traffic before sending out a ping.

• PingTimeout = Time interval to wait for a ping response after a ping is sent before failing a connection.

• ConnFailTimeout = Time interval to wait before failing SCSI commands back to an application for unsuccessful commands.

• AbortTimeout = Time interval to wait for a abort command to complete before declaring the abort command failed.

• ResetTiemout = Time interval to wait for a reset command to complete before declaring the reset command failed.

• InitialR2T = Enabling/disabling of R2T flow control with the target.

• MaxRecvDataSegmentLength = Maximum number of bytes that the initiator can receive in an iSCSI PDU.

• FirstBurstLength = Maximum number of bytes of unsolicited data the initiator is allowed to send.

• MaxBurstLength = Maximum number of bytes for the SCSI payload negotiated by initiator.

• TCPWindowSize = Maximum number of bytes that can be sent over a TCP connection by the initiator before receiving an

acknowledgement from the target.

• Continuous = Enabling/disabling the discovery session to be kept alive.

A detailed description for each of these parameters is included in both the man page and the included sample iscsi.conf file.Please consult these sources for examples and more detailed programming instructions.----------------------------iSCSI COMMANDS AND UTILITIES----------------------------This section gives a description of all the commands and utilities available with the iSCSI driver.- "iscsi-ls" lists information about the iSCSI devices available to the driver. Please refer to the man page for more information.



LUN ManagementLUN Basics

Simply stated, a LUN is a logical entity that converts raw physical disk space into logical storage space that a host server's operatingsystem can access and use. Any computer user recognizes the logical drive letter that has been carved out of their disk drive. For example, a computer may boot from the C: drive and access file data from a different D: drive. LUNs do the same basic job. "LUNsdifferentiate between different chunks of disk space. "A LUN is part of the address of the storage that you're presenting to a [host]server."

LUNs are created as a fundamental part of the storage provisioning process using software tools that typically accompany the particulastorage platform. However, there is not a 1-to-1 ratio between drives and LUNs. Numerous LUNs can easily be carved out of a singledisk drive. For example, a 500 GB drive can be partitioned into one 200 GB LUN and one 300 GB LUN, which would appear as twounique drives to the host server. Conversely, storage administrators can employ Logical Volume Manager software to combine multipleLUNs into a larger volume. Veritas Volume Manager from Symantec Corp. is just one example of this software. In actual practice, disksare first gathered into a RAID group for larger capacity and redundancy (e.g., RAID-50), and then LUNs are carved from that RAIDgroup.

LUNs are often referred to as logical "volumes," reflecting the traditional use of "drive volume letters," such as volume C: or volume F:on your computer. But some experts warn against mixing the two terms, noting that the term "volume" is often used to denote the largevolume created when multiple LUNs are combined with volume manager software. In this context, a volume may actually involvenumerous LUNs and can potentially confuse storage allocation. "The 'volume' is a piece of a volume group, and the volume group iscomposed of multiple LUNs,"Once created, LUNs can also be shared between multiple servers. For example, a LUN might be shared between an active and

standby server. If the active server fails, the standby server can immediately take over. However, it can be catastrophic for multipleservers to access the same LUN simultaneously without a means of coordinating changed blocks to ensure data integrity. Clusteringsoftware, such as a clustered volume manager, a clustered file system, a clustered application or a network file system using NFS or CIFS, is needed to coordinate data changes.

SAN zoning and masking

LUNs are the basic vehicle for delivering storage, but provisioning SAN storage isn't just a matter of creating LUNs or volumes; theSAN fabric itself must be configured so that disks and their LUNs are matched to the appropriate servers. Proper configuration helps tomanage storage traffic and maintain SAN security by preventing any server from accessing any LUN.Zoning makes it possible for devices within a Fibre Channel network to see each other. By limiting the visibility of end devices, servers(hosts) can only see and access storage devices that are placed into the same zone. In more practical terms, zoning allows certainservers to see one or more ports on a disk array. Bandwidth, and thus minimum service levels, can be reserved by dedicating certainports to a zone or isolate incompatible ports from one another.Consequently, zoning is an important element of SAN security and high-availability SAN design. Zoning can typically be broken down

into hard and soft zoning. With hard zoning, each device is assigned to a zone, and that assignment can never change. In soft zoning,the device assignments can be changed by the network administrator.LUN masking adds granularity to this concept. Just because you zone a server and disk together doesn't mean that the server shouldbe able to see all of the LUNs on that disk. Once the SAN is zoned, LUNs are masked so that each host server can only see specificLUNs. For example, suppose that a disk has two LUNs, LUN_A and LUN_B. If we zoned two servers to that disk, both servers wouldsee both LUNs. However, we can use LUN masking to allow one server to see only LUN_A and mask the other server to see onlyLUN_B. Port-based LUN masking is granular to the storage array port, so any disks on a given port will be accessible to any servers onthat port. Server-based LUN masking is a bit more granular where a server will see only the LUNs assigned to it, regardless of the otherdisks or servers connected.

LUN scaling and performanceLUNs are based on disks, so LUN performance and reliability will vary for the same reasons. For example, a LUN carved from a FibreChannel 15K rpm disk will perform far better than a LUN of the same size taken from a 7,200 rpm SATA disk. This is also true of LUNsbased on RAID arrays where the mirroring of a RAID-0 group may offer significantly different performance than the parity protection of aRAID-5 or RAID-6/dual parity (DP) group. Proper RAID group configuration will have a profound impact on LUN performance.An organization may utilize hundreds or even thousands of LUNs, so the choice of storage resources has important implications for thestorage administrator. Not only is it necessary to supply an application with adequate capacity (in gigabytes), but the LUN must also bedrawn from disk storage with suitable characteristics. "We go through a qualification process to understand the requirements of theapplication that will be using the LUNs for performance, availability and cost," For example, a LUN for a mission-critical databaseapplication might be taken from a RAID-0 group using Tier-1 storage, while a LUN slated for a virtual tape library (VTL) or archiveapplication would probably work with a RAID-6 group using Tier-2 or Tier-3 storage.

LUN management toolsA large enterprise array may host more than 10,000 LUNs, so software tools are absolutely vital for efficient LUN creation, manipulationand reporting. Fortunately, management tools are readily available, and almost every storage vendor provides some type of management software to accompany products ranging from direct-attached storage (DAS) devices to large enterprise arrays.Administrators can typically opt for vendor-specific or heterogeneous tools. A data center with one storage array or a single-vendor shop would probably do well with the indigenous LUN management tool that accompanied their storage system. Multivendor shopsshould at least consider heterogeneous tools that allow LUN management across all of the storage platforms. Mack uses EMC



ControlCenter for LUN masking and mapping, which is just one of several different heterogeneous tools available in the marketplace.While good heterogeneous tools are available, he advises caution when selecting a multiplatform tool. "Sometimes, if the tool is writtenby a particular vendor, it will manage 'their' LUNs the best," he says. "LUNs from the other vendors can take the back seat -- themanagement may not be as well integrated."In addition to vendor support, a LUN management tool should support the entire storage provisioning process. Features should includemapping to specific array ports and masking specific host bus adapters (HBA), along with comprehensive reporting. The LUNmanagement tool should also be able to reclaim storage that is no longer needed. Although a few LUN management products supportautonomous provisioning, experts see some reluctance toward automation. "It's hard to do capacity planning when you don't have anychecks and balances over provisioning," Mack says, also noting that automation can circumvent strict change control processes in an

IT organization.

LUNs at work

Significant storage growth means more LUNs, which must be created and managed efficiently while minimizing errors, reigning in costsand maintaining security. For Thomas Weisel Partners LLC, an investment firm based in San Francisco, storage demands have simplyexploded to 80 terabytes (TB) today -- up from about 8 TB just two years ago. Storage continues to flood the organization's data center at about 2 TB to 3 TB each month depending on projects and priorities.This aggressive growth pushed the company out of a Hitachi Data Systems (HDS) storage array and into a 3PARdata Inc. S400system. LUN deployment starts by analyzing realistic space and performance requirements for an application. "Is it something thatneeds a lot of fast access, like a database or something that just needs a file share?" asks Kevin Fiore, director of engineering servicesat Thomas Weisel. Once requirements are evaluated, a change ticket is generated and a storage administrator provisions theresources from a RAID-5 or RAID-1 group depending on the application. Fiore emphasizes the importance of provisioning efficiency,noting that the S400's internal management tools can provision storage in just a few clicks.Fiore also notes the importance of versatility in LUN management tools and the ability to move data. "Dynamic optimization allows me

to move LUNs between disk sets," he says. Virtualization has also played an important role in LUN management. VMware has allowedFiore to consolidate about 50 servers enterprise-wide along with the corresponding reduction in space, power and cooling. this lets theorganization manage more storage with less hardware.LUNs getting largeAs organizations deal with spiraling storage volumes, experts suggest that efficiency enhancing features, such as automation, willbecome more important in future LUN management. Experts also note that virtualization and virtual environments will play a greater role in tomorrow's LUN management. For example, it's becoming more common to provision very large chunks of storage (500 GB to 1TB or more) to virtual machines. "You might provision a few terabytes to a cluster of VMware servers, and then that storage will beprovisioned out over time.

How to merge two switches with different active zone sets??How to merge two switches with different active zone sets."

Merging Two B-series Directors and/or Switches with Different Active Zoning Configurations

Before Beginning The following procedure is disruptive to fabric traffic.:--It will require disabling the switch and the removal of the effective zoning configurations at one step. Removing this configuration willstop the data flow. Since this step in the procedure takes only a few moments to complete, data should resume as soon as the newconfiguration is activated.To evaluate the impact on an OS platforms and applications, please refer to the ESN Topology Guide for OS platform timeoutrecommendations as well as the actual configuration files of the servers to identify their current timeout settings.

Supported Director and Switch TypesThe following information on fabric merging applies to the following EMC Director and Switch types:ED-12000BDS-32B2DS-16B2DS-16BDS-8BNOTE: Also applies to similar OEM version of these switch types. See ESM for latest switch firmware qualification prior to merging non-

EMC Directors and/or Switches into an EMC SAN.

Host Requirements:A host computer with a FTP service is required.

Merging

1. Log into the first switch via telnet or WebToolsa. Known as “swo1” for this exampleb. For DS-16Bs, DS-8Bs, and comparable switch models running firmware 2.5.0d and above, default access zoning must be set to“ALLACCESS”NOTE: This is an offline command that wi ll interrupt data flow.1. Issue switchdisable command2. Issue configure command



3. Enter “y” when prompted for “Zoning Operation parameters”4. Enter “1” when prompted for “Default Access”5. Enter “n” for all other parameters6. Issue switchenable command2. Upload the first switch (or one switch of a multi-switch fabric) configuration to a host using FTPa. Use configupload command or use WebToolsb. Name the file “sw01_config.txt”1. All zoning and configuration data for this switch will be located in this file.3. Log into the second switch via telnet or WebTools

a. Known as “sw02” for this exampleb. For DS-16Bs, DS-8Bs, and comparable switch models running firmware 2.5.0d and above, default access zoning must be set to“ALLACCESS”NOTE: This is an offline command that wi ll interrupt data flow.1. Issue switchdisable command2. Issue configure command3. Enter “y” when prompted for “Zoning Operation parameters”4. Enter “1” when prompted for “Default Access”5. Enter “n” for all other parameters6. Issue switchenable command4. Upload the switch configuration to a host using FTPa. Use configupload command or use WebToolsb. Name the file “sw02_config.txt”1. All zoning and configuration data for this switch will be located in this file.5. Open in a text editor (i.e. Microsoft Word, VI, emacs, etc) for both “sw01_config.txt” and “sw02_config.txt” files

a. The uploaded configuration contains a list of switches in the fabric, list of ISLs, list of ports, name server data, and zoninginformation.b. For the purposes of merging, one need only be concerned with the zoning section of the uploaded configuration, which may be foundat the end of the file. It contains zones, aliases, and defined and effective configurations.

Example sw01_config.txt Zoning Section[Zoning]cfg.cfg_1:zone_1zone.zone_1:10:00:00:08:00:00:00:01alias.HBA1:10:00:00:08:00:00:00:01enable:cfg_1Example sw02_config.txt Zoning Section[Zoning]cfg.cfg_2:zone_2zone.zone_2:10:00:00:00:09:00:00:02

alias.HBA2:10:00:00:00:09:00:00:02enable:cfg_2

6. Make a copy of “sw01_config.txt” and rename the copy as “configmerge.txt”7. Copy aliases from “sw02_config.txt”a. Highlight and copy the alias data8. Paste aliases from “sw02_config.txt” to “configmerge.txt”a. Paste under existing alias data in “configmerge.txt”9. Copy zones from “sw02_config.txt”a. Highlight and copy the zone data10. Paste zones from “sw02_config.txt” to “configmerge.txt”a. Paste under existing zone data in “configmerge.txt”11. Copy zone names from “cfg.cfg” line of “[Zoning]” section from “sw02_config.txt” to “configmerge.txt”a. Copy zone name(s) to “cfg.cfg” line after existing zones separating each zone with a semicolonb. The last zone name will not be followed by a semicolon

Example Configmerge.txt Zoning Section After Paste from sw02_config.txt[Zoning]cfg.cfg_1:zone_1;zone_2zone.zone_1:10:00:00:08:00:00:00:01zone.zone_2:10:00:00:00:09:00:00:02alias.HBA1:10:00:00:08:00:00:00:01alias.HBA2:10:00:00:00:09:00:00:02enable:cfg_1

NOTE: Areas highlighted in red above illustrate the additions from “sw02_config.txt”12. Save changes to “configmerge.txt”13. Download “configmerge.txt” to sw01a. Use configdownload command or use WebTools



1. If using configdownload command, the switch must be manually disabled before downloading commences. Use the switchdisablecommand. After completion, the switch must be manually enabled. Use the switchenable command.2. Using WebTools automatically disables and re-enables the switch.b. After downloading, the newly merged configuration is automatically the effective configuration because it is already specified in the“[Zoning]” section as the enabled configuration.14. Issue cfgsave command on sw01a. Saves the configuration to flash15. Issue cfgshow command to see defined and effective zoning configurationsExample Output of cfgshow Command on sw01 After Configmerge.txt is Downloaded

Defined configuration:cfg: cfg_1 zone_1; zone_2zone: zone_1 10:00:00:08:00:00:00:01zone: zone_2 10:00:00:00:09:00:00:02alias: HBA1 10:00:00:08:00:00:00:01alias: HBA2 10:00:00:00:09:00:00:02Effective configuration:cfg: cfg_1zone: zone_1 Protocol:ALL 10:00:00:08:00:00:00:01zone: zone_2 Protocol:ALL 10:00:00:00:09:00:00:02

16. On sw02, issue the following commands to remove both defined and effective zoning configurationsa. cfgdisableb. cfgclear

c. cfgsave17. Issue cfgshow command to see defined and effective zoning configurationsExample Output of “cfgshow” Command on Second Switch After Removing the ConfigurationDefined configuration:no configuration definedEffective configuration:no configuration in effect18. Connect the switches via a fiber optic cable to the ports chosen to be E_ports.a. sw02 will inherit the zoning data from sw01 when they exchange fabric parameters.NOTE: Be sure to check that both switches have unique Domain IDs. Be sure to check the fabric parameters such as EDTOV, RATOV,Data Field Size, Core Switch PID are identical.19. Issue cfgshow command on second switch to see defined and effective zoning configurations.Example Output of cfgshow Command on sw02 After Fabric Merge

Defined configuration:

cfg: cfg_1 zone_1; zone_2zone: zone_1 10:00:00:08:00:00:00:01zone: zone_2 10:00:00:00:09:00:00:02alias: HBA1 10:00:00:08:00:00:00:01alias: HBA2 10:00:00:00:09:00:00:02Effective configuration:cfg: cfg_1zone: zone_1 Protocol:ALL 10:00:00:08:00:00:00:01zone: zone_2 Protocol:ALL 10:00:00:00:09:00:00:02

NOTE: Zoning configurations on both switches are now identical.20. Issue switchshow and fabricshow commands to verify a successful fabric merge

Hope this info will help you to replace a switch in your enviornment or merge.

Overview of RAID Striping

Very simply, RAID striping is a means of improving the performance of large storage systems. For most normal PCs or laptops, files arestored in their entirety on a single disk drive, so a file must be read from start to finish and passed to the host system. With largestorage arrays, disks are often organized into RAID groups that can enhance performance and protect data against disk failures.Striping is actually RAID-0; a technique that breaks up a file and interleaves its contents across all of the disks in the RAID group. Thisallows multiple disks to access the contents of a file simultaneously. Instead of a single disk reading a file from start to finish, stripingallows one disk to read the next stripe while the previous disk is passing its stripe data to the host system -- this enhances the overalldisk system performance, which is very beneficial for busy storage arrays.



- 64 Total ports- 4 ports reserved for card failure- 4 ports reserved for E_ports- 56 ports remaining.-(int(56/5)) No more than 4:1 ratio, hosts : fa-45 Possible host connections-/ 2 to support multi-pathing22 host connections (gain of 11)

Three switches

- 96 total ports- 4 ports reserved for card failure- 12 ports reserved for E_ports-80 ports remaining- (int(80/5)) No more than 4:1 ratio, hosts : fa-64 Possible host connections-/ 2 to support multi-pathing-32 host connections (gain of 10)

Four switches-128 total ports- 4 ports reserved for card failure

- 24 ports reserved for E_ports-100 ports remaining- (int(100/5)) No more than 4:1 ratio, hosts : fa-80 Possible host connections- / 2 to support multi-pathing-40 host connections (gain of 8)

Putting in that fourth connectrix means that you gain only 8 host connections from a 32 port connectrix switch.

Kashya :- Advances in Data Protection and ReplicationKashya (EMC Acquired last year ) develops unique algorithmic technologies to enable an order of magnitude improvement in the reliability, cost, and performance of an enterprise’s data protection

capabilities. Based on the Kashya Data Protection Appliance platform, Kashya’s powerful solutionsdeliver superior data protection at a fraction of the cost of existing solutions. Kashya’s Data ProtectionAppliance connects to the SAN and IP infrastructure and provides bi-directional replication across anydistance for heterogeneous storage, SAN, and server environments.

The recent Storage industry challange is minimize downtime and how to keep business running 24 X7 X 365. The data that drives today’s globally oriented businesses is stored on large networks of interconnected computers and data storage devices. This data must be 100% available and alwaysaccessible and up-to-date, even in the face of local or regional disasters. Moreover, these conditionsmust be met at a cost that is affordable, and without in any way hampering normal companyoperations.

To reduce the business risk of an unplanned event of this type, an enterprise must ensure that a copyof its business-critical data is stored at a secondary location. Synchronous replication, used soeffectively to create perfect copies in local networks, performs poorly over longer distances.

Replication Method:

1) Synchronous – Every write transaction committed must be acknowledged from thesecondary site. This method enables efficient replication of data within the localSAN environment.



2) Asynchronous – Every write transaction is acknowledged locally and then added to aqueue of writes waiting to be sent to the secondary site. With this method, somedata will normally be lost in the event of a disaster. This requires the samebandwidth as a synchronous solution.

3) Snapshot –A consistent image of the storage subsystem is periodically transferred to the

secondary site. Only the changes made since the previous snapshot must be transferred, resulting insignificant savings in bandwidth. By definition, this solution produces a copy that is not up-to-date;however, increasing the frequency of the snapshots can reduce the extent of this lag.

4) Small-Aperture Snapshot – Kashya’s system offers the unique ability to take frequent snapshots, just seconds apart. This innovative feature is utilized to minimize the risk of data loss due to data corruption that typically follows

rolling disasters.

Kashya’s advanced architecture can be summarized as follows:

• Positioning atθ the junction between the SAN and the IP infrastructure enables Kashya

solutions to:

• Deploy enterprise-class data protection♣ non-disruptively and non-invasivel

• Support heterogeneous server, SAN, and♣ storage platforms

• Monitor SAN and WAN behavior on an ongoing basis, to♣ maximize the data

protection process

• Advanced algorithms, that:-θ Automatically manage the replication process, with strict

adherence to userdefined policies that are tied to user-specified business objectives

SAN Zoning in details

Lets discuss about most important thing in SAN environment ZONING. Zoning is the only way to restrict access for storage to all thehost. We will be discussing about Zoning in details.

There are two type of Zoning basically : Hard Zoning and Soft Zoning. Lets first define what is Zoning??

Zoning is nothing but map of host to device to device connectivity is overlaid on the storage networking fabric, reducing the risk of unauthorized access.Zoning supports the grouping of hosts, switches, and storage on the SAN, limiting access between members of one zone and resources in another.

Zoning also restricts the damage from unintentional errors that can corrupt storage allocations or destabilize the network. For example,if a Microsoft Windows server is mistakenly connected to a fabric dedicated to UNIX applications, the Windows server will write header information to each visible LUN, corrupting the storage for the UNIX servers. Similarly, Fibre Channel register state change notifications(RSCN) that keep SAN entities apprised of configuration changes, cansometimes destabilize the fabric. Under certain circumstances, an RSCN storm will overwhelm a



Different Vendor Worldwide Names WWN Details

Vendor Worldwide Names WWN :

Twenty-four of the sixty-four bit •World Wide Name• must be unique for every vendor. A partial listing of those vendors most familiar toEMC with regard to Symmetrix Fibre Channel connectivity.

If decoding a HBA WWN, then issue an 8f, command to view the WWN in the FA login table. Bytes 1-3 of the World Wide Namescontain the unique vender codes. Note that if there is a switch connected between the FA and the host bus adapter, then the name andfabric servers of the switch will login to the FA. These WWNs can be decoded in the same way as the HBA WWNs.

In the following example the unique vendor code is 060B00, this indicates that the HBA attached was supplied by Hewlett Packard.

UTILITY 8F -- SCSI Adapter utility : TIME: APR/23/01 01:23:30------------------------------------

HARD LOOP ID : 000 (ALPA=EF) LINK STATE : ONLINE: LOOPCHIP TYPE/REV: 00/00 Q RECS TOTAL: 3449 CREDIT: 0 RCV BUFF SZ: 2048

IF FLAGS : 01/ TAGD/NO LINK/NO SYNC/NO WIDE/NO NEGO/NO SOFT/NO ENVT/NO CYLNIF FLAGS1: 08/NO PBAY/NO H300/NO RORD/ CMSN/NO QERR/NO DQRS/NO DULT/NO SUNPIF FLAGS2: 00/NO SMNS/NO DFDC/NO DMNQ/NO NFNG/NO ABSY/NO SQNT/NO NRSB/NO SVASIF FLAGS3: 00/NO SCI3/NO ..../NO ..../NO ..../NO ..../NO ..../NO ..../NO ....

FC FLAGS : 57/ ARRY/ VOLS/ HDAD/NO HDNP/ GTLO/NO PTOP/ WWN /NO VSAFC FLAGS1: 00/NO VCM /NO CLS2/NO OVMS/NO ..../NO ..../NO ..../NO ..../NO ....FC FLAGS2: 00/NO ..../NO ..../NO ..../NO ..../NO ..../NO ..../NO ..../NO ....FC FLAGS3: 00/NO ..../NO ..../NO ..../NO ..../NO ..../NO ..../NO ..../NO ....

HOST SID PORT NAME (WWN) NODE NAME RCV BUF CREDIT CLASS-----------------------------------------------------------------------------000001 50060B0000014932 50060B0000014933 992 EE 4 3PRLI REQ: IFN RXDDONE.

The following are common HBA vendor codes:

Refer to the open systems host matrix if you need to know whether these HBAs are supported for specific hosts.

00-00-D1 (hex) ADAPTEC INCORPORATED0000D1 (base 16) ADAPTEC INCORPORATED

00-30-D3 (hex) Agilent Technologies0030D3 (base 16) Agilent Technologies

00-60-69 (hex) BROCADE COMMUNICATIONS SYSTEMS006069 (base 16) BROCADE COMMUNICATIONS SYSTEMS

00-02-A5 (hex) Compaq Computer Corporation

0002A5 (base 16) Compaq Computer Corporation

00-60-48 (hex) EMC CORPORATION006048 (base 16) EMC CORPORATION

00-00-C9 (hex) EMULEX CORPORATION0000C9 (base 16) EMULEX CORPORATION

00-E0-24 (hex) GADZOOX NETWORKS00E024 (base 16) GADZOOX NETWORKS

00-60-B0 (hex) HEWLETT-PACKARD CO.0060B0 (base 16) HEWLETT-PACKARD CO.



00-50-76 (hex) IBM005076 (base 16) IBM

00-E0-69 (hex) JAYCOR NETWORKS, INC.00E069 (base 16) JAYCOR NETWORKS, INC.

08-00-88 (hex) MCDATA CORPORATION080088 (base 16) MCDATA CORPORATION

08-00-0E (hex) NCR CORPORATION08000E (base 16) NCR CORPORATION

00-E0-8B (hex) QLOGIC CORP.00E08B (base 16) QLOGIC CORP.

00-00-6B (hex) SILICON GRAPHICS INC./MIPS00006B (base 16) SILICON GRAPHICS INC./MIPS,00-10-9B (hex) VIXEL CORPORATION00109B (base 16) VIXEL CORPORATIONThis information will help you to identify the vendor of particularar HBA's WWN.

How VERITAS Dynamic Multi-Pathing (DMP) works with a CLARiiONarray?DMP With CLARiiON:-

CLARiiON arrays are active-passive devices that allow only one path at a time to be used for I/O. The path that is used for I/O is calledthe active or primary path. An alternate path (or secondary path) is configured for use in the event that the primary path fails. If theprimary path to the array is lost, DMP automatically routes I/O over the secondary path or other available primary paths.

For active/passive disk arrays, VxVM uses the available primary path as long as it is accessible. DMP shifts I/O to the secondary pathonly when the primary path fails. This is called "failover" or "standby" mode of operation for I/O. To avoid the continuous transfer of ownership of LUNs from one controller to another, which results in a severe slowdown of I/O, do not access any LUN on other than theprimary path (which could be any of four available paths on a FC4700 and CX-Series arrays).

Note: DMP does not perform load balancing across paths for active-passive disk arrays.

DMP failover functionality is supported and should attempt to limit any scripts or processes from using the passive paths to theCLARiiON array. This will prevent DMP from causing unwanted LUN trespasses.

To view potential trespasses, look at the ktrace (kt_std) information from SPcollect, messages similar the following can be seenhappening with regularity.

09:07:31.995 412 820f6440 LUSM Enter LU 34 state=LU_SHUTDOWN_TRESPASS09:07:35.970 203 820f6440 LUSM Enter LU 79 state=LU_SHUTDOWN_TRESPASS09:07:40.028 297 820f6440 LUSM Enter LU 13 state=LU_SHUTDOWN_TRESPASS09:07:42.840 7 820f6440 LUSM Enter LU 57 state=LU_SHUTDOWN_TRESPASS

The "Enter LU ##" is the decimal array LUN number one would see in the Navisphere Manager browser. When the messages occur,there will be no 606 trespass messages in the SP event logs. This is an indication that thetrespasses are the 'masked out' DMPtrespass messages. Executing I/Os to the /dev/dsk device entry will cause this to happen.

Using the SPcollect SP_navi_getall.txt file, check the storagegroup listing to find out which hosts these LUNs belong to. Then obtainan EMCGrab/EMCReport from the affected hosts and you will need to look for a host-based process that could potentially be sendingI/O down the 'passive' path. Those I/Os can be caused by performance scripts, format or devfsadm commands being run or even hostmonitoring software that polls all device paths.One workaround is to install and configure EMC PowerPath. PowerPath disables the auto trespass mode and is designed to handle I/Orequests properly so that the passive path is not used unless required. This will require changing the host registration parameter "failover mode" to a '1'. This failover mode is termed an "explicit mode" and it will resolve the type of trespass issues noted above.

Setting Failover Values for Initiators Connected to a Specific Storage System:

Navisphere Manager lets you edit or add storage system failover values for any or all of the HBA initiators that are connected to astorage system and displayed in the Connectivity Status dialog box for that storage system.

1. In the Enterprise Storage dialog box, navigate to the icon for the storage system whose failover properties you want to add or edit.2. Right-click the storage system icon, and click Connectivity Status.3. In the Connectivity Status dialog box, click Group Edit to open the Group Edit Initiators dialog box.4. Select the initiators whose New Initiator Information values you want to add or change, and then add or edit the values in Initiator Type, ArrayCommPath and Failover Mode.5. Click OK to save the settings and close the dialog box.Navisphere updates the initiator records for the selected initiators, and registers any unregistered initiators.

Background Verify and Trespassing

Background Verify must be run by the SP that currently owns the LUN. Trespassing is a means of transferring current ownership of aLUN from one SP to the other. Therefore, aborting a Background Verify is part of the trespass operation – it is a necessary step.

LSAN Zonng (Logical SAN)An LSAN is a Logical Storage Area Network that spans multiple Physical fabrics and allows specified devices from these autonomousfabrics to communicate with each other without merging the physical fabrics. In other word, A logical network that spans multiplephysical fabrics. It allows specified devices from the autonomous fabric to communicate with each other using a FC router withoutmerging the physical fabrics.- A LSAN zone is a traditional zone with a special naming convention.- Zone names must start with “LSAN_” or “lsan_” or “LSan_”- LSAN zones are architecturally comaptiable with FOS and M-EOS- FC Router uses LSAN zones to determine which devices need to be exported/imported into which routed fabrics.- LSAN zones must be configured in all fabrics where the shared physical devices exist.- The router performs zoning enforcement for edge fabrics at the ingress Router EX Port.

LSAN Implementation Rules:

- LSAN zone members must be defined using the device Port WWN, Zone members, including aliases, need to be defined usingWWPN.- LSAN zone name on the routed fabrics do not need to be identical, but is recommended for ease of administration andtroubleshooting.- LSAN zones in routed fabrics sharing devices are not required to have identical membership. Shared devices must exist in bothfabrics LSAN zones.

Once the LSAN zones are enabled, you will be able to check status of LSAN zones and members from the FC Router using the

command lsanzoneshow –s

Router:admin>lsanzoneshow –sFabric ID: 1 Zone Name: lsan_zone110:00:00:00:98:23:12:11 Exist10:00:00:00:98:23:ab:cd Imported

Fabric ID: 2 Zone Name: lsan_zone110:00:00:00:98:23:12:11 Imported10:00:00:00:98:23:ab:cd Exist

The output reveals what devices are “Exported (Exist) and Imported from all the routed fabrics.

Switch Interoperability LimitationMDS Interoperability Mode Limitations

When a VSAN is configured for the default interoperability mode, the MDS 9000 Family ofswitches is limited in the following areas when interoperating with non-MDS switches:

• Interop mode only affects the specified VSAN. The MDS 9000 switch canstill operate with full functionality in other non-interop mode VSANs. All switches thatpartake in the interoperable VSAN should have that VSAN set to interop mode, even if they do not have any end devices.

• Domain IDs are restricted to the 97 to 127 range, to accommodateMcData's nominal restriction to this same range. Domain IDs can either be set upstatically (the MDS 9000 switch will only accept one domain ID; if it does not get thatdomain ID, it isolates itself from the fabric), or preferred (if the MDS 9000 switch doesnot get the requested domain ID, it takes any other domain ID).

• TE ports and PortChannels cannot be used to connect an MDS 9000

switch to a non-MDS switch. Only E ports can be used to connect an MDS 9000 switch toa non-MDS switch. However, TE ports and PortChannels can still be used to connect anMDS 9000 switch to other MDS 9000 switches, even when in interop mode.

• Only the active zone set is distributed to other switches.

• In MDS SAN-OS Release 1.3(x), Fibre Channel timers can be set on a perVSAN basis. Modifying the times, however, requires the VSAN to be suspended. Prior toSAN-OS Release 1.3, modifying timers required all VSANs across the switch to be put intothe suspended state.

• The MDS 9000 switch still supports the following zoning limits per switchacross all VSANs:

– 2000 zones (as of SAN-OS 3.0, 8000 zones)

– 20000 aliases

– 1000 zone sets

– 20000 members

– 8000 LUN members

– 256 LUN members per zone/alias

Brocade Interoperability Mode Limitations

When interoperability mode is set, the Brocade switch has the following limitations:

• All Brocade switches should be in Fabric OS 2.4 or later.

• Interop mode affects the entire switch. All switches in the fabric musthave interop mode enabled.

•  Msplmgmtdeactivate must be run prior to connecting the Brocadeswitch to either an MDS 9000 switch or a McData switch. This command uses Brocadeproprietary frames to exchange platform information. The MDS 9000 switch and McDataswitches do not understand these proprietary frames, and rejection of these framescauses the common E ports to become isolated.

• Enabling interoperability mode is a disruptive process to the entireswitch. It requires the switch to be rebooted.

• If there are no zones defined in the effective configuration, the defaultbehavior of the fabric is to allow no traffic to flow. If a device is not in a zone, it isisolated from other devices.

• Zoning can only be done with pWWNs. You cannot zone by port numbersor nWWNs.

• To manage the fabric from a Brocade switch, all Brocade switches mustbe interconnected. This interconnection facilitates the forwarding of the inactive zoneconfiguration.

•  Domain IDs are restricted to the 97 to 127 range toaccommodate McData's nominal restriction to this same range.

• Brocade WebTools will show a McData switch or an MDS 9000 switch asan anonymous switch. Only a zoning configuration of the McData switch or the MDS 9000switch is possible.

• Private loop targets will automatically be registered in the fabric usingtranslative mode.

• Fabric watch is restricted to Brocade switches only.

• The full zone set (configuration) is distributed to all switches in thefabric. However, the full zone set is distributed in a proprietary format, which onlyBrocade switches accept. Other vendors reject these frames, and accept only the activezone set (configuration).

• The following services are not supported:

– The Alias Server

Registering HBAs With the Storage SystemRegistering Fibre Channel HBAs or iSCSI NICs with the storage system enables the storage system to see the HBAs or NICs. Toregister HBAs or NICs with the storage system, you will start or restart the Navisphere Agent on the host.Microsoft WindowsTo register the host’s HBAs with the storage system, start the Navisphere Agent as follows:1. On the Windows host, right click My Computer and select Manage.2. Click Services and Applications and then click Services.3. Find EMC Navisphere Agent service.4. If already started, stop the EMC Navisphere Agent service.5. Start the EMC Navisphere Agent service.

AIXTo register the host’s HBAs with the storage system, on the AIX host, stop and start the Navisphere Agent. For example:

# rc.agent stop# rc.agent start

HP-UXTo register the host’s HBAs with the storage system, on the HP-UX host, stop and start the Navisphere Agent. For example:

# /sbin/init.d/agent stop# /sbin/init.d/agent start

LinuxTo register the host’s HBAs with the storage system, on the Linux host, stop and start the Navisphere Agent. For example:



# /etc/init.d/naviagent stop# /etc/init.d/naviagent start

NetWareTo register the host’s HBAs with the storage system, on the NetWare host, restart the Navisphere Agent. In the NetWare server consolescreen, enter:

sys:\emc\agent\navagent.nlm -f

sys:\emc\agent\agent.cfg

SolarisTo register the host’s HBAs with the storage system, on the Solaris host, stop and start the Navisphere Agent. For example:

# /etc/init.d/agent stop# /etc/init.d/agent start

VMware ESX server 2.5.0 and later To register the host’s HBAs with the storage system, on the VMware host, stop and start the Navisphere Agent. For example:

# /etc/init.d/agent stop# /etc/init.d/agent start

EMC PowerPath Pseudo DevicesLets first disuss what is Powerpath software. If you are familiar with EMC product and then definitelly will be using EMC Powerpathsoftware.Those who are new to storage world, it will interesting to know about this product as there are only few software in this category likeDMP,PVLINK, LVM etc from other vendor. This sofware is one of the most robust compare to other, thats reason EMC generationgmore revenue out of this Product.... So, not tooooo much marketttin :)))EMC PowerPath software is Host/Server based failover software, what is that mean failover. failover can be anything likeserver,HBA,Fabric etc. If you have fully licenced package in your enviornment then you will have all capability. Most important not leastthis software got good feature like dynamic IO Loading and Automatic Failure detection which is missing in other product. Basically inshort we can define that EMC PowerPath provides you to have HA configuration. EMC Powerpath slogan is like "set it and forget".EMC PowerPath features a driver residing on the host above HBA Device Layer. This transparent componenet allows PowerPath tocreate Virtual(power) devices that provide failure resistant and load balanced paths to storage systems. An application needs only toreference a virt ual device while Powerpath manages path allocation to storage system.

With PowerPath, the route between server and storage system can assume a complex path. One powerpath device include as many as32 physical I/O paths ( 16 for Clariion), with each path designated to the operating system by different name.

In most cases, the application must be reconfigured to use pseudo devices, otherwise PowerPath load balancing and path failover functionality will not be available.

The following describe whether application need to be reconfigure to use pseudo devices.1) Windows Plateform :- No. ( Application not require to reconfigured to use Pseudo Devices )2) AIX :- NO- For LVM, Yes, if applicaiton do not use LVM3) HP-UX - NO4) Solaris :- Yes, Incluing filesystem mounting tables and volume managers.5) Linux :- Same as Solaris



if you attach new LUN to Host, powerpath automatically detect that LUN if you have exposedcorrectly and create device name like emcpower1c, emcpower2c etc, even when you type commandon CLI like#powermt display dev=all;you will be able to device entry like emcpowerN.....Hope this will help you to understand why powerpath uses pseudo devices?

Fibre Channel SAN Configuration Rules

Single-initiator zoning rule :--Each HBA port must be in a separate zone that contains it and the SP ports with which it communicatesEMC recommends single-initiator zoning as a best practice.Fibre Channel fan-in rule:--A server can be zoned to a maximum of 4 storage systems.Fibre Channel fan-out rule:-The Navisphere software license determines the number of servers you can connect to a CX3-10c, CX3-20c,CX3-20f, CX3-40c, CX3-40f, or CX3-80 storage systems. The maximum number of connections between servers and a storagesystem is defined by the number of initiators supported per storage-system SP. An initiator is an HBAport in a that can access a storage system. Note that some HBAs have multiple ports. Each HBA port that is zoned to an SP port is onepath to that SP and the storage system containing that SP. Depending on the type of storage system and the connections between itsSPs and the switches, an HBA port can be zoned through different switch ports to the same SP port or to different SP ports, resulting inmultiple paths between the HBA port and an SP and/or the storage system. Note that the failover software running on the server maylimit the number of paths supported from the server to a single storage-system SP and from a server to the storage system.

Storage systems with Fibre Channel data ports :- CX3-10c (SP ports 2 and 3), CX3-20c (SP ports 4 and 5), CX3-20f (all ports),CX3-40c (SP ports 4 and 5), CX3-40f (all ports), CX3-80 (all ports).Number of servers and storage systems As many as the available switch ports, provided each server follows the fan-in rule above andeach storage system follows the fan-out rule above, using WWPN switch zoning.Fibre connectivityFibre Channel Switched Fabric (FC-SW) connection to all server types.Fibre Channel switch terminologySupported Fibre Channel switches.Fabric - One or more switches connected by E_Ports. E_Ports are switch ports that are used only for connecting switches together.ISL - (Inter Switch Link). A link that connects two E_Ports on two different switches.Path - A path is a connection between an initiator (such as an HBA port) and a target (such as an SP port in a storage system). EachHBA port that is zoned to a port on an SP is one path to that SP and the storage system containing that SP. Depending on the type of

storage system and the connections between its SPs and the switch fabric, an HBA port can be zoned through different switch ports tothe same SP port or to different SP ports, resulting in multiple paths between the HBA port and an SP and/or the storage system. Notethat the failover software running on the server may limit the number of paths supported from the server to a single storage-systemSP and from a server to the storage system.

EMC PowerPath Migration Enabler PowerPath Migration Enabler is a host-based software product that enables other technologies, such as array-basedreplication and virtualization, to eliminate -application downtime during data migrations or virtualizationimplementations. PowerPath Migration Enabler allows EMC Open Replicator for Symmetrix and EMC Invista customersto eliminate downtime during data migrations from EMC storage to Symmetrix, and during virtualized deployments toInvista.. PowerPath Migration Enabler—which leverages the same underlying technology as PowerPath—keeps arraysin synch during Open Replicator for Symmetrix data migrations, with minimal impact to host resources. It also enablesseamless deployment of Invista virtualized environments by encapsulating (or bringing under its control) the volumes

that will be virtualized. In addition,EMC PowerPath boasts the following benefits:

PowerPath Migration Enabler with Open Replicator for Symmetrix:¨ Eliminates planned downtime¨ Provides flexibility in time to perform migrationPowerPath Migration Enabler with EMC Invista:¨ Eliminates planned downtime¨ Eliminates need for data copy and additional storage for data migration¨ I/O redirection allows Administrators to “preview” deployment without committing to redirection



Differences between a SnapView clone, Mirror, and snapshot?

Most of user asked me what are basic differences between EMC Clone/Mirror/Snapshot? This is really confusing terminology becausemost of things will be same logically.Only thing change that is implementation and purpose of uses. I am trying to write basic andcommon differences:

1) A clone is a full copy of data in a source LUN. A snapshot is a point-in time "virtual" copy that does not occupy any diskspace.2) A snapshot can be created or destroyed in seconds, unlike a clone or mirror. A clone, for example, can take minutes tohours to create depending on the size of the source LUN.3) A clone or mirror requires exactly the same amount of disk space as the source LUN. A snapshot cache LUN generallyrequires approximately 10% to 20% of the source LUN size.4) A clone is an excellent on-array solution that enables you to recover from a data corruption issue. Mirrors are designed for off-site data recovery.5) A clone is typically fractured after it is synchronized while a mirror is not fractured but instead is actively and continuouslybeing synchronized to any changes on the source LUN.Clones and mirrors are inaccessible to the host until they are fractured. Clones can be easily resynchronized in either direction. Thiscapability is not easily implemented with mirrors.Restoring data after a source LUN failure is instantaneous using clones after a reverse synchronization is initialized. Restore time froma snapshot depends on the time it takes to restore from the network or from a backup tape.Once a clone is fractured, there is no performance impact (that is, performance is comparable to the performance experienced with a

conventional LUN). For snapshots, the performance impact is above average and constant due to copy on first write (COFW).

I left one more term EMC BCV(Business Continuity Volume). It is totally different concept thought. I will try to cover in upcoming postthough I have discussed about EMC BCV in my older post. But it is more or less cloning only only implementation change.

EMC BCV Operation on Host running Oracle Database

Here I am going to discuss about TimeFinder BCV Split operation where Host running on Oracle Database. This split operation isdifferent from normal BCV split operation. There are differences in command as well. Thats reason I am putting steps for this:

The following steps describes splitting BCV devices that hold a database supporting a host running an Oracle database. In this case,the BCV split operation is in an environment without PowerPath or ECA. The split operation described here suspends writes to adatabase momentarily while an instant split occurs. After an establish operation and the standard device and BCV mirrors are

synchronized, the BCV device becomes a mirror copy of the standard device. You can split the paired devices to where each holdsseparate valid copies of the data, but will no longer remain synchronized to changes when they occur.

The Oracle database is all held on standard and BCV devices assigned to one Oracle device group.

1) Check device status on the database BCVsTo view and check status of the database BCV pairs, use the following form:

symmir –g DgName query

Check the output to ensure all BCV devices listed in the group are in the synchronized state

2) Check and set the user account

For SYMCLI to access a specified database, set the SYMCLI_RDB_CONNECT environment variable to the username and password of

the system administrator’s account. The export action sets this variable to a username of system and a password of manager, allowinga local connection as follows:

export SYMCLI_RDF_CONNECT=system/manager

The ORACLE_HOME command specifies the location of the Oracle binaries and the ORACLE_SID command specifies the databaseinstance name as follows:

export ORACLE_HOME=/disks/symapidvt/oraclhome/api179export ORACLE_sid=api179

You can test basic database connectivity with the symrdb command as follows:

symrdb list –type oracle



3) Backup the database

For safety, perform a database hot backup. For example:

symioctl begin backup –type oracle –nop

4) Freeze the databaseFor safety, perform a freeze on the database I/O. For example:

symioctl freeze –type oracle –nop

This command suspends writes to the Oracle database.

5) Split all BCV devices in the groupTo split all the BCV devices from the standard devices in the database device group, enter:

symmir –g oraclegrp split –instant -noprompt

Make sure the split operation completes on all BCVs in the database device group.

6) Thaw the database to resume I/OTo allow writes to the database to resume for normal operation, enter:

symioctl thaw –type oracle –nop

7) End the backupTo terminate the hot backup mode, enter the following command:

symioctl end backup –type oracle –nop

EMC PowerPath Pseudo DevicesLets first disuss what is Powerpath software. If you are familiar with EMC product and then definitelly will be using EMC Powerpathsoftware.

Those who are new to storage world, it will interesting to know about this product as there are only few software in this category likeDMP,PVLINK, LVM etc from other vendor. This sofware is one of the most robust compare to other, thats reason EMC generationgmore revenue out of this Product.... So, not tooooo much marketttin :)))EMC PowerPath software is Host/Server based failover software, what is that mean failover. failover can be anything likeserver,HBA,Fabric etc. If you have fully licenced package in your enviornment then you will have all capability. Most important not leastthis software got good feature like dynamic IO Loading and Automatic Failure detection which is missing in other product. Basically inshort we can define that EMC PowerPath provides you to have HA configuration. EMC Powerpath slogan is like "set it and forget".EMC PowerPath features a driver residing on the host above HBA Device Layer. This transparent componenet allows PowerPath tocreate Virtual(power) devices that provide failure resistant and load balanced paths to storage systems. An application needs only toreference a virt ual device while Powerpath manages path allocation to storage system.

With PowerPath, the route between server and storage system can assume a complex path. One powerpath device include as many as32 physical I/O paths ( 16 for Clariion), with each path designated to the operating system by different name.

In most cases, the application must be reconfigured to use pseudo devices, otherwise PowerPath load balancing and path failover functionality will not be available.



The following describe whether application need to be reconfigure to use pseudo devices.1) Windows Plateform :- No. ( Application not require to reconfigured to use Pseudo Devices )2) AIX :- NO- For LVM, Yes, if applicaiton do not use LVM3) HP-UX - NO4) Solaris :- Yes, Incluing filesystem mounting tables and volume managers.5) Linux :- Same as Solarisif you attach new LUN to Host, powerpath automatically detect that LUN if you have exposed correctly and create device name likeemcpower1c, emcpower2c etc, even when you type command on CLI like#powermt display dev=all;

you will be able to device entry like emcpowerN.....Hope this will help you to understand why powerpath uses pseudo devices?

What are the differences between failover modes on a CLARiiONarray?

What are the differences between failover modes on a CLARiiON array?

A CLARiiON array is an Active/Passive device and uses a LUN ownership model. In other words, when a LUN is bound it has a defaultowner, either SP-A or SP-B. I/O requests traveling to a port SP-A can only reach LUNs owned by SP-A and I/O requests traveling to aport on SP-B can only reach LUNs owned SP-B. It is necessary to have different failover methods because in certain situations a hostwill need to access a LUN on the non-owning SP.

The following failover modes apply:

Failover Mode 0 –

LUN Based Trespass Mode This failover mode is the default and works in conjunction with the Auto-trespass feature. Auto-trespass is amode of operation that is set on a LUN by LUN basis. If Auto-Trespass is enabled on the LUN, the non-owning SP will report that theLUN exists and is available for access. The LUN will trespass to the SP where the I/O request is sent. Every time the LUN is trespasseda Unit Attention message is recorded. If Auto-trespass is disabled, the non-owning SP will report that the LUN exists but it is notavailable for access. If an I/O request is sent to the non-owning SP, it is rejected and the LUN’s ownership will not change.Note: The combination of Failover Mode 0 and Auto-Trespass can be dangerous if the host is sending I/O requests to both SP-A andSP-B because the LUN will need to trespass to fulfill each request. This combination is most commonly seen on an HP-UX server usingPV-Links. The Auto-trespass feature is enabled through the Initiator Type setting of HP-AutoTrespass. A host with no failover software

should use the combination of Failover Mode 0 and Auto-trespass disabled.

Failover Mode 1 – Passive Not Ready Mode In this mode of operation the non-owning SP will report that all non-owned LUNs existand are available for access. Any I/O request that is made to the non-owning SP will be rejected. A Test Unit Ready (TUR) commandsent to the non-owning SP will return with a status of device not ready. This mode is similar to Failover Mode 0 with Auto-Trespassdisabled. Note: This mode is most commonly used with PowerPath. To a host without PowerPath, and configured with Failover Mode 1,every passive path zoned, for example, a path to SP-B for a LUN owned by SP-A, will show to the server as Not Ready. This will showas with offline errors on a Solaris server, SC_DISK_ERR2 errors with sense bytes 0102, 0700, and 0403 on an AIX server or buffer toI/O errors on a Linux server. If PowerPath is installed, these types of messages should not occur.

Failover Mode 2 – DMP Mode In this mode of operation the non-owning SP will report that all non-owned LUNs exist and are availablefor access. This is similar to Failover Mode 0 with Auto-trespass Enabled. Any I/O requests made to the non-owning SP will cause theLUN to be trespassed to the SP that is receiving the request. The difference between this mode and Auto-trespass mode is that UnitAttention messages are suppressed. Note: This mode is used for some Veritas DMP configurations on some operating systems.

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Because of the similarities to Auto-Trespass, this mode has been known to cause “Trespass Storms.” If a server runs a script thatprobes all paths to the Clariion, for instance format on a Solaris server, the LUN will trespass to the non owning SP when the I/Orequest is sent there. If this occurs for multiple LUNs, a significant amount of trespassing will occur.

Failover Mode 3 – Passive Always Ready Mode In this mode of operation the non-owning SP will report that all non-owned LUNs existand are available for access. Any I/O requests sent to the Non-owning SP will be rejected. This is similar to Failover Mode 1. However,any Test Unit Ready command sent from the server will return with a success message, even to the non-owning SP. Note: This mode isonly used on AIX servers under very specific configuration parameters and has been developed to better handle a CLARiiON non-disruptive upgrade (NDU) when AIX servers are attached.

Restrictions & recommendations for binding disks into LUNs:LUN to bind Restrictions and recommendations ----------- Any LUN You can bind only unbound disk modules. All disk modules in amust have the same capacity to fully use the modules' storage space.--- In AX-series storage systems, binding disks into LUNs is not supported.RAID 5 - You must bind a minimum of three and no more than sixteen disk modules. We recommend you bind five modules for moreefficient use of disk space. In a storage system with SCSI disks, you should use modules on different SCSI buses for highestavailability. *RAID 3 - You must bind exactly five or nine disk modules in a storage system with Fibre Channel disks and exactly five disk modules ina storage system with SCSI disks. In a storage system with SCSI disks, you should use modules on separate SCSI buses for highestavailability. You cannot bind a RAID 3 LUN until you have allocated storage-system memory for the LUN, unless on a FC4700 or CX-series *IMPORTANT: RAID 3, non FC4700/CX-series does not allow caching, therefore, when binding RAID 3 LUNS, the -c cache-flags switch

do not applyRAID 1 - You must bind exactly two disk modules. *RAID 0 - You must bind a minimum of three and no more than sixteen disk modules. If possible in a storage system with SCSI disks,use modules on different SCSI buses for highest availability. *RAID 1/0 - You must bind a minimum of four but no more than sixteen disk modules, and it must be an even number of modules.Navisphere Manager pairs modules into mirrored images in the order in which you select them. The first and second modules youselect are a pair of mirrored images; the third and fourth modules you select are another pair of mirrored images; and so on. The firstmodule you select in each pair is the primary image, and the second module is the secondary image. If possible in a storage systemwith SCSI disks the modules you select for each pair should be on different buses for highest availability. *individual disk unit none

RAID-6 New Protection on DMX-4 With Enginuity 5772 code

RAID 6 Protection

RAID 6 was implemented to provide superior data protection, tolerating up to two drive failures in the same RAID group. Other RAIDprotection schemes, such as mirroring (RAID 1), RAID S, and RAID 5, protect a system from a single drive failure in a RAID group.RAID 6 provides this extra level of protection while keeping the same dollar cost per megabyte of usable storage as RAID 5configurations. Although two parity drives are required for RAID 6, the same ratio of data to parity drives is consistent. For example, aRAID 6 6+2 configuration consists of six data segments and two parity segments. This is equivalent to two sets of a RAID 5 3+1configuration, which is three data segments and one parity segment, so 6+2 = 2(3+1).

When to use different RAID Type?

As we know that we have different type of RAID but all the raid type are not suitable for the all application. We select raid typedepending on the application and IO load/Usages. Actually there are so many factor involved before you select suitable raid type for any application. I am trying to give brief idea in order to select best raid type for any application. You can select raid type depending onyour environment.

When to Use RAID 5RAID 5 is favored for messaging, data mining, medium-performance media serving, and RDBMS implementations in which the DBA iseffectively using read-ahead and write-behind. If the host OS and HBA are capable of greater than 64 KB transfers, RAID 5 is acompelling choice.These application types are ideal for RAID 5:1) Random workloads with modest IOPS-per-gigabyte requirements2) High performance random I/O where writes represent 30 percent or less of the workload3) A DSS database in which access is sequential (performing statistical analysis on sales records)4) Any RDBMS table space where record size is larger than 64 KB and access is random (personnel records with binary content, such

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as photographs)5) RDBMS log activity6) Messaging applications7) Video/Media

When to Use RAID 1/0RAID 1/0 can outperform RAID 5 in workloads that use very small, random, and write-intensive I/O—where more than 30 percent of theworkload is random writes. Some examples of random, small I/O workloads are:1) High-transaction-rate OLTP

2) Large messaging installations3) Real-time data/brokerage records4) RDBMS data tables containing small records that are updated frequently (account balances)5) If random write performance is the paramount concern, RAID 1/0 should be used for these applications.

When to Use RAID 3RAID 3 is a specialty solution. Only five-disk and nine-disk RAID group sizes are valid for CLARiiON RAID 3. The target profile for RAID3 is large and/or sequential access.Since Release 13, RAID 3 LUNs can use write cache. The restrictions previously made for RAID 3—single writer, perfect alignment withthe RAID stripe—are no longer necessary, as the write cache will align the data. RAID 3 is now more effective with multiple writingstreams, smaller I/O sizes (such as 64 KB) and misaligned data.RAID 3 is particularly effective with ATA drives, bringing their bandwidth performance up to Fibre Channel levels.

When to Use RAID 1With the advent of 1+1 RAID 1/0 sets in Release 16, there is no good reason to use RAID 1. RAID 1/0 1+1 sets are expandable,whereas RAID 1 sets are not.

Different RAID ExplainedRAID is a redundant array of independent disks (originally redundant array of inexpensive disks). RAID is a way of storing thesame data in different places (thus, redundantly) on multiple hard disks. By placing data on multiple disks, I/O (input/output)operations can overlap in a balanced way, which improves performance. Since multiple disks increases the mean timebetween failures (MTBF), storing data redundantly also increases fault tolerance.A RAID appears to the operating system as a single logical hard disk. RAID employs the technique of disk striping, whichinvolves partitioning each drive's storage space into units ranging from a sector (512 bytes) up to several megabytes. Thestripes of all the disks are interleaved and addressed in order.In a single-user system where large records, such as medical or other scientific images, are stored, the stripes are typicallyset up to be small (perhaps 512 bytes) so that a single record spans all disks and can be accessed quickly by reading alldisks at the same time. In a multi-user system, better performance requires establishing a stripe wide enough to hold thetypical or maximum size record. This allows overlapped disk I/O across drives.There are at least nine types of RAID, as wellas a non-redundant array (RAID-0).RAID-0:This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.RAID-1:This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping.Read performance is improved since either disk can be read at the same time. Write performance is the same as for single diskstorage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.RAID-2:This type uses striping across disks with some disks storing error checking and correcting (ECC) information. It has no advantage over RAID-3.

RAID-3:This type uses striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used todetect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives.Since an I/O operation addresses all drives at the same time, RAID-3 cannot overlap I/O. For this reason, RAID-3 is best for single-usersystems with long record applications.RAID-4:This type uses large stripes, which means you can read records from any single drive. This allows you to take advantage of overlappedI/O for read operations. Since all write operations have to update the parity drive, no I/O overlapping is possible. RAID-4 offers noadvantage over RAID-5.RAID-5:This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can beoverlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which dofew write operations.



RAID-6:This type is similar to RAID-5 but includes a second parity scheme that is distributed across different drives and thus offers extremelyhigh fault- and drive-failure tolerance.RAID-7:This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of astand- alone computer. One vendor offers this system.RAID-10:Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost.There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In

RAID-1+0, the data is mirrored and the mirrors are striped.RAID-50 (or RAID-5+0):This type consists of a series of RAID-5 groups and striped in RAID-0 fashion to improve RAID-5 performance without reducing dataprotection.RAID-53 (or RAID-5+3):This type uses striping (in RAID-0 style) for RAID-3's virtual disk blocks. This offers higher performance than RAID-3 but at much highercost.RAID-S (also known as Parity RAID):This is an alternate, proprietary method for striped parity RAID from EMC Symmetrix that is no longer in use on current equipment. Itappears to be similar to RAID-5 with some performance enhancements as well as the enhancements that come from having a high-speed disk cache on the disk array.

What is LUN_Z or LUNz?

Lets discuss about LUNz/LUN_Z in Operating System specially in CLARiiON environment. We know that what is LUN?? LUN is nothingbut logical slice of disc which stands for Logical Unit Number. This terminology comes with SCSI-3 group, if you want to know more justvisit www.t10.org and www.t11.org

A SCSI-3 (SCC-2) term defined as "the logical unit number that an application client uses to communicate with, configure anddetermine information about an SCSI storage array and the logical units attached to it. The LUN_Z value shall be zero." In theCLARiiON context, LUNz refers to a fake logical unit zero presented to the host to provide a path for host software to send configurationcommands to the array when no physical logical unit zero is available to the host. When Access Logix is used on a CLARiiON array, anagent runs on the host and communicates with the storage system through either LUNz or a storage device. On a CLARiiON array, theLUNZ device is replaced when a valid LUN is assigned to the HLU LUN by the Storage Group. The agent then communicates throughthe storage device. The user will continue, however, to see DGC LUNz in the Device Manager.LUNz has been implemented on CLARiiON arrays to make arrays visible to the host OS and PowerPath when no LUNs are bound onthat array. When using a direct connect configuration, and there is no Navisphere Management station to talk directly to the array over IP, the LUNZ can be used as a pathway for Navisphere CLI to send Bind commands to the array.LUNz also makes arrays visible to the host OS and PowerPath when the host’s initiators have not yet ‘logged in to the Storage Groupcreated for the host. Without LUNz, there would be no device on the host for Navisphere Agent to push the initiator record through tothe array. This is mandatory for the host to log in to the Storage Group. Once this initiator push is done, the host will be displayed as anavailable host to add to the Storage Group in Navisphere Manager (Navisphere Express).LUNz should disappear once a LUN zero is bound, or when Storage Group access has been attained.To turn on the LUNz behavior onCLARiiON arrays, you must configure the "arraycommpath.

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