Guide Lines

Speak slowly and clearly Do not speak loudly Be confident with your answers Do not argue with the interviewer Accept your mistakes Ask him to repeat the question if it is not clear Preserve professional conversation (Politely and Friendly) Be confident and positive Before you go to the interview go through your resume properly Before you attend the interview study about the organization

What are the day to day activities in your current profile?

Explain about day to day activities in your current profile.

Example: Monitoring alerts using Monitoring Tool like EMC Control Center Follow-up for the pending service requests Checking ticketing tool for any new tickets Updating the tickets with the current status Responding to the assigned service requests Documenting the service request solutions Performing Health checks Preparing Job plans for changes Participating bridge calls if any Attending internal/customer meetings, etc

Explain about roles and responsibilities in your current profile

Example: Providing L2 support for the EMC DMX and Clariion storage Performing upgrades/downgrades of Firmware Storage Provisioning for new hosts Storage Provisioning/ reclamation for existing hosts Performing Zoning Troubleshooting Switch issues Troubleshooting storage issues Troubleshooting Performance issues

Vendor /customer management during the hardware failure issues Performing Changes and preparing job plans for changes Performing TimeFinder/Mirror Operations Performing SRDF Operations Troubleshooting failed SRDF/TimeFinder jobs Monitoring Storage environment using Monitoring Tools (ECC) Preparing Storage Capacity planning reports Performing Disaster Recovery Activities.etc

What is the first thing you will do at office?

Example: Checking the mails for any escalations/ alerts/ new assignments Checking the monitoring tools for any critical alerts on console Checking the ticketing tools for newly logged service requests Checking the pending issues.etc.,

Explain about your current storage environment like about Arrays, Connectivity, Replication technology, DR environment, Management tools, Monitoring tools, etc.,

Example: We are having One Data Center and One DR Center and 16 branch offices. In Data Center and DR Center we have 2 Symmetrix DMX-4 Arrays; each box is having 800TB of data. For backup purpose we are creating mirrors in data center using TimeFinder/Mirror technology and for local/fast restoration we are creating snaps using TimeFinders/SNAP technology. For remote replication (remote backup and DR purpose) we are using SRDF/S technology. Each Brach offices are having CX series Clariion Arrays, For backup purpose we are creating SnapView Clones and for fast/local restoration we are creating SnapView Snapshots. We are using symcli for storage operation for DMX Arrays and Navisphere Manager for Clariion Arrays, Connectrix Manager for switch directors management, cli for individual brocade switches, for monitoring storage environment, Storage Scope reporting, performance monitoring

we are using EMC Control Center, Replication Manager for automating the TimeFinder/Mirror operations, Power path for path redundancy at host-end. Connectivity between the Data center and DR center is over Fibre Channel. Connectivity between the branch offices and DC/DR is over Ethernet

Explain whatever management tools you are using.

Example: We are using Symcli/SMC/ECC for DMX Arrays storage provisioning We are using Navisphere Manager for Clariion storage provisioning We are using connectrix manager for Directors management We are using cli/GUi for Individual switches management We are using EMC Control Center for Alerts management/monitoring We are using EMC Control Center for Storage Scope reporting We are using EMC Control Center for Performance Monitoring We are using Replication Manager for automating the TimeFinder/Mirror/Clone jobs We are using symcli for managing and monitoring SRDF jobs We are using Power path for path management at host end

How are you monitoring your Storage environment?

Explain about the Monitoring tools using in your organization

Example: EMC Control Center, etc

How are you getting the tickets/service requests?

Explain ticketing tools using in your organization.

Example: Getting tickets through telephone Getting tickets through emails Getting tickets in ticketing tool Self logged tickets (if we found any critical alerts on management tool, we create tickets our self), etc.,

Explain step by step procedure to close the received ticket?

Explain about ticket closure procedure in your current organization.

Example: Received the tickets/Service requests/Service orders via telephone/ mails/ web portal, etc.

Ticket Priority (S1/S2/S3 or P0/P1/P2/P3) Customer/ Helpdesk/ Service desk will set the priority.

Engineer will work on ticket, once it is resolved he will take the confirmation/ approval to close the ticket from the end user who hasraised the ticket and will update the ticket with the findings and resolution then he will close the ticket.

If not resolved: Lack of Experience /un-known problem Change Required Hardware failure

Lack of Experience/ Unknown problem: Inform to helpdesk or whoever assigned the ticket to you for escalation with your findings?

Change Required Update the ticket with your findings Inform to the end user, server/device owner Raise a change request if you are responsible or inform to owner to raise the change request Coordinate with all teams who are all involved in this change Schedule the change and get it done Update and close the ticket after getting the confirmation from the end user

Hardware failure: Inform your findings to the end user Provide work around/alternate solution for time being if possible Update the ticket with the progress Check whether this failure can be done by internal team or vendor support is required If vendor support is required log a service request with the vendor

If yes take the necessary approvals from server/device owner, team lead or who ever involved Schedule the change as per approvals Inform to vendor about change schedule and get it resolved the problem Once it is resolved check with the users who are affected with this problem and take the confirmation/approval to close the ticket Update the ticket and close

When you initiate the change what are your responsibilities?

Explain about the procedure you are following in your current organization.

Example: Whenever it is required to perform the change, I will inform to my Manager and will take approval to proceed further. I will prepare the job plan for the change. I will raise the change request with the schedule timings and will take the necessary approvals from concerned teams who will affect with this change. I will perform the change according to the job plan. I will cross check all operation running smoothly? I will take the confirmation from all teams. I will update the change request and will close.

Tell me one critical situation you have handled?

Explain about a critical situation which you have handled in the present job.

Why do you want to leave your present organization?

Tell him the reason why do you want to leave the present company, keep in mind that the answer should be positive.

Example: Career growth. Change of location necessity. Expecting large scope of work, etc.,

Why do you want to join in this organization?

Explain why you want to join in this organization

Example: This organization is having 100,000 employees

So many years of existence in the industry

There are lot of opportunities for career growth in this Organization,

re there any questions you would like to ask us?

Ask one or two questions if you want a clarification on any topic during interview

Example: Can you please tell me the project details Working location and Shift timings May I know the storage environment in this project? What will be the scope of work of mine in this project How is the career growth in your organization, etc.,

SAN INTERVIEW QUESTION AND ANSWER

Can you describe SAN in your won word?

A storage area network (SAN) is a high-speed special-purpose network (or subnetwork) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. Typically, a storage area network is part of the overall network of computing resources for an enterprise. A storage area network is usually clustered in close proximity to other computing resources such as IBM Power5 boxes but may also extend to remote locations for backup and archival storage, using wide area network carrier technologies such as ATM or SONET.

A storage area network can use existing communication technology such as IBMs optical fiber ESCON or it may use the newer Fibre Channel technology. Some SAN system integrators liken it to the common storage bus (flow of data) in a personal computer that is sharedby different kinds of storage devices such as a hard disk or a CD-ROM player.

SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data migration from one storage device to another, and

the sharing of data among different servers in a network. SANs can incorporate subnetworks with network-attached storage (NAS) systems.

So you mention NAS, but what is NAS?

Network-attached storage (NAS) is hard disk storage that is set up with its own network address rather than being attached to the department computer that is serving applications to a networks workstation users. By removing storage access and its management from the department server, both application programming and files can be served faster because they are not competing for the same processor resources. The network-attached storage device is attached to a local area network (typically, an Ethernet network) and assigned an IP address. File requests are mapped by the main server to the NAS file server.

Network-attached storage consists of hard disk storage, including multi-disk RAID systems, and software for configuring and mapping file locations to the network-attached device. Network-attached storage can be a step toward and included as part of a more sophisticated storage system known as a storage area network (SAN).

NAS software can usually handle a number of network protocols, including Microsofts Internetwork Packet Exchange and NetBEUI, Novells Netware Internetwork Packet Exchange, and Sun Microsystems Network File System. Configuration, including the setting of user access priorities, is usually possible using a Web browser.

What is SMTP and how it works?

SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP, which let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving e-mail. On Unix-based systems, sendmail is the most widely-used SMTP server for e-mail. A commercial package, Sendmail, includes a POP3 server. Microsoft Exchange includes an SMTP server and can also be set up to include POP3 support.

SMTP usually is implemented to operate over Internet port 25.

Do you have any idea about NAT?

Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.

NAT serves three main purposes:

Provides a type of firewall by hiding internal IP addresses Enables a company to use more internal IP addresses. Since

theyre used internally only, theres no possibility of conflict with IP addresses used by other companies and organizations.

Allows a company to combine multiple ISDN connections into a single Internet connection.

Explain DHCP and its uses to an environment?

Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the devices IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task. This means that a new computer can be added to a network without the hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP addressing for dial-up users.

What does SNMP stands for?

Short for Simple Network Management Protocol, a set of protocols for managing complex networks. SNMP works by sending messages, called Protocol Data Units, to different parts of a network. SNMP-compliant devices, called Agents, store data about themselves in Management Information Bases and return this data to the SNMP requesters.

What do you know about TCPDump?

TCPDump is a common computer network debugging tool that runs under the command line. It allows the user to intercept and display TCP/IP and other packets being transmitted or received over a network

to which the computer is attached. TCPDump works on most Unix-like platforms: Linux, Solaris, BSD, Mac OS X, HP-UX and AIX among others. On Windows, WinDump can be used; its a port of tcpdump to Windows.

You must have a root or super user authority to use TCPdumps in UNIX like environment.

What is software RAID Levels do?Redundant Arrays of Independent Disks (RAID) is formally defined as a method to store data on any type of disk medium.

LDAP

The Light Directory Access Protocol (LDAP) defines a standard method for accessing and updating information in a directory (a database) either locally or remotely in a client-server model.

What are the benefits of fibre channel SANs?

Fibre Channel SANs are the de facto standard for storage networking in the corporate data center because they provide exceptional reliability, scalability, consolidation, and performance. Fibre Channel SANs provide significant advantages over direct-attached storage through improved storage utilization, higher data availability, reduced management costs, and highly scalable capacity and performance.

What environment is most suitable for fibre channel SANs?

Typically, Fibre Channel SANs are most suitable for large data centers running business-critical data, as well as applications that require high-bandwidth performance such as medical imaging, streaming media, and large databases. Fibre Channel SAN solutions can easily scale to meet the most demanding performance and availability requirements.

What customer problems do fibre channel SANs solve?

The increased performance of Fibre Channel enables a highly effective backup and recovery approach, including LAN-free and server-free backup models. The result is a faster, more scalable, and more reliable backup and recovery solution. By providing flexible connectivity options and resource sharing, Fibre Channel SANs also greatly reduce the number of physical devices and disparate systems that must be purchased and managed, which can dramatically lower capital

expenditures. Heterogeneous SAN management provides a single point of control for all devices on the SAN, lowering costs and freeing personnel to do other tasks.

How long has fibre channel been around?

Development started in 1988, ANSI standard approval occurred in 1994, and large deployments began in 1998. Fibre Channel is a mature, safe, and widely deployed solution for high-speed (1 GB, 2 GB, 4 GB) communications and is the foundation for the majority of SAN installations throughout the world.

What is the future of fibre channel SANs?

Fibre Channel is a well-established, widely deployed technology with a proven track record and a very large installed base, particularly in high-performance, business-critical data center environments. Fibre Channel SANs continue to grow and will be enhanced for a long time to come. The reduced costs of Fibre Channel components, the availability of SAN kits, and the next generation of Fibre Channel (4 GB) are helping to fuel that growth. In addition, the Fibre Channel roadmap includes plans to double performance every three years.

What are the benefits of 4gb fibre channel?

Benefits include twice the performance with little or no price increase, investment protection with backward compatibility to 2 GB, higher reliability due to fewer SAN components (switch and HBA ports) required, and the ability to replicate, back up, and restore data more quickly. 4 GB Fibre Channel systems are ideally suited for applications that need to quickly transfer large amounts of data such as remote replication across a SAN, streaming video on demand, modeling and rendering, and large databases. 4 GB technology is shipping today.

How is fibre channel different from ISCSI?

Fibre Channel and iSCSI each have a distinct place in the IT infrastructure as SAN alternatives to DAS. Fibre Channel generally provides high performance and high availability for business-critical applications, usually in the corporate data center. In contrast, iSCSI is generally used to provide SANs for business applications in smaller regional or departmental data centers.

When should I deploy fibre channel instead of ISCSI?

For environments consisting of high-end servers that require high bandwidth or data center environments with business-critical data, Fibre Channel is a better fit than iSCSI. For environments consisting of many midrange or low-end servers, an IP SAN solution often delivers the most appropriate price/performance.

Name some of the SAN topologies?

Point-to-point, arbitrated loop, and switched fabric topologies.

Whats the need for separate network for storage why LAN cannot be used?

LAN hardware and operating systems are geared to user traffic, and LANs are tuned for a fast user response to messaging requests.

With a SAN, the storage units can be secured separately from the servers and totally apart from the user network enhancing storage access in data blocks (bulk data transfers), advantageous for server-less backups.

What are the advantages of RAID?

Redundant Array of Inexpensive Disks

Depending on how we configure the array, we can have the- data mirrored [RAID 1] (duplicate copies on separate drives)- striped [RAID 0] (interleaved across several drives), or- parity protected [RAID 5](extra data written to identify errors).

These can be used in combination to deliver the balance of performance and reliability that the user requires.

Define RAID? Which one you feel is good choice?

RAID (Redundant array of Independent Disks) is a technology to achieve redundancy with faster I/O. There are Many Levels of RAID to meet different needs of the customer which are: R0, R1, R3, R4, R5, R10, R6.

Generally customer chooses R5 to achieve better redundancy and speed and it is cost effective.R0 Striped set without parity/[Non-Redundant Array].Provides improved performance and additional storage but no fault

tolerance. Any disk failure destroys the array, which becomes more likely with more disks in the array. A single disk failure destroys the entire array because when data is written to a RAID 0 drives, the data is broken into fragments. The number of fragments is dictated by the number of disks in the drive. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, giving this type of arrangement huge bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss

R1 Mirrored set without parity.Provides fault tolerance from disk errors and failure of all but one of the drives. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning. Using RAID 1 with a separate controller for each disk is sometimes called duplexing.

R3 Striped set with dedicated parity/Bit interleaved parity.This mechanism provides an improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes. The single parity disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.

R4 Block level parity.Identical to RAID 3, but does block-level striping instead of byte-level striping. In this setup, files can be distributed between multiple disks. Each disk operates independently which allows I/O requests to be performed in parallel, though data transfer speeds can suffer due to the type of parity. The error detection is achieved through dedicated parity and is stored in a separate, single disk unit.

R5 Striped set with distributed parity.Distributed parity requires all drives but one to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.

R6 Striped set with dual distributed Parity.Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high availability systems. This becomes increasingly important because large-capacity drives lengthen the time needed to recover from the failure of a single drive. Single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt: the larger the drive, the longer the rebuild will take. Dual parity gives time to rebuild the array without the data being at risk if one drive, but no more, fails before the rebuild is complete.

What is the difference between RAID 0+1 and RAID 1+0?

RAID 0+1 (Mirrored Stripped)

In this RAID level all the data is saved on stripped volumes which are in turn mirrored, so any disk failure saves the data loss but it makes whole stripe unavailable. The key difference from RAID 1+0 is that RAID 0+1 creates a second striped set to mirror a primary striped set. The array continues to operate with one or more drives failed in the same mirror set, but if drives fail on both sides of the mirror the data on the RAID system is lost. In this RAID level if one disk is failed full mirror is marked as inactive and data is saved only one stripped volume.

RAID 1+0 (Stripped Mirrored)In this RAID level all the data is saved on mirrored volumes which are in turn stripped, so any disk failure saves data loss. The key difference from RAID 0+1 is that RAID 1+0 creates a striped set from a series of mirrored drives. In a failed disk situation RAID 1+0 performs better because all the remaining disks continue to be used. The array can sustain multiple drive losses so long as no mirror loses both its drives.This RAID level is most preferred for high performance and high data protection because rebuilding of RAID 1+0 is less time consuming in comparison to RAID 0+1.

When JBODs are used?

Just a Bunch of Disks

It is a collection of disks that share a common connection to the server, but dont include the mirroring,striping, or parity facilities that RAID systems do, but these capabilities are available with host-based software.

Differentiate RAID & JBOD?

RAID: Redundant Array of Inexpensive DisksFault-tolerant grouping of disks that server sees as a single disk volume

Combination of parity-checking, mirroring, striping

Self-contained, manageable unit of storage

JBOD: Just a Bunch of Disks

Drives independently attached to the I/O channelScalable, but requires server to manage multiple volumes

Do not provide protection in case of drive failure

What is a HBA?

Host bus adapters (HBAs) are needed to connect the server (host) to the storage.

What are the advantages of SAN?

Massively extended scalability.

Greatly enhanced device connectivity.Storage consolidation.LAN-free backup.Server-less (active-fabric) backup.Server clustering.Heterogeneous data sharing.Disaster recovery Remote mirroring.While answering people do NOT portray clearly what they mean & what advantages each of them have, which are cost effective & which are to be used for the clients requirements.

What is the difference b/w SAN and NAS?

The basic difference between SAN and NAS, SAN is Fabric based and NAS is Ethernet based.SAN Storage Area NetworkIt accesses data on block level and produces space to host in form of disk.

NAS Network attached StorageIt accesses data on file level and produces space to host in form of shared network folder.

What is a typical storage area network consists of if we consider it for implementation in a small business setup?

If we consider any small business following are essentials components of SAN:

Fabric Switch.FC Controllers.JBODs.

Can you briefly explain each of these Storage area components?

Fabric Switch: Its a device which interconnects multiple network devices .There are switches starting from 16 port to 32 ports which connect 16 or 32 machine nodes etc. vendors who manufacture these kind of switches are Brocade, McData.

What is the most critical component in SAN?

Each component has its own criticality with respect to business needs of a company.

How is a SAN managed?

There is much management software used for managing SANs to name a few:

Santricity.IBM Tivoli Storage Manager.CA Unicenter.Veritas Volumemanger.

Which one is the Default ID for SCSI HBA?

Generally the default ID for SCSI HBA is 7.

SCSI- Small Computer System Interface.

HBA Host Bus Adaptor.

What is the highest and lowest priority of SCSI?

There are 16 different IDs which can be assigned to SCSI device 7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, 8.

Highest priority of SCSI is ID 7 and lowest ID is 8.

How do you install device drivers for the HBA first time during OS installation?

In some scenarios you are supposed to install Operating System on the drives connected thru SCSI HBA or SCSI RAID Controllers, but most of the OS will not be updated with drivers for those controllers, that time you need to supply drivers externally, if you are installing windows, you need to press F6 during the installation of OS and provide the driver disk or CD which came along with HBA.

If you are installing Linux you need to type linux dd for installing any driver.

What is Array?

Array is a group of Independent physical disks to configure any Volumes or RAID volumes.

Can you describe at-least 3 troubleshooting scenarios which you have come across in detail?

SCENARIO 1: How do you find/debug when there is error while working SCSI devices?

In our daily SAN troubleshooting there are many management and configuration tools we use them to see when there is a failure with target device or initiator device.

Some time it is even hard to troubleshoot some of the things such as media errors in the drives, or some of the drives taking long time to spin-up. In such cases these utilities will not come to help. To debug this kind of information most of the controller will be implemented with 3-pin serial debug port. With serial port debug connector cable you can collect the debug information with hyper terminal software.

SCENARIO 2: I am having an issue with a controller its taking lot of time to boot and detect all the drives connected how can I solve this.?There are many possibilities that might cause this problem. One of the

reason might be you are using bad drives that cannot be repaired. In those cases you replace the disks with working ones.

Another reason might be slots you connected your controller to a slot which might not be supported.Try to connect with other types of slots.

One more probable reason is if you have flashed the firmware for different OEMs on the same hardware.To get rid of this the flash utilities will be having option to erase all the previous and EEPROM and boot block entry option. Use that option to rectify the problem.

SCENARIO 3: I am using tape drive series 700X, even the vendor information on the Tape drive says 700X, but the POST information while booting the server is showing as 500X what could be the problem?

First you should make sure your hardware is of which series, you can find out this in the product website.Generally you can see this because in most of the testing companies they use same hardware to test different series of same hardware type. What they do is they flash the different series firmware. You can always flash back to exact hardware type.

Which are the 4 types of SAN architecture types?

Core-edge.

Full-Mesh.

Partial-Mesh.

Cascade.

Which command is used in Linux to know the driver version of any hardware device?

dmesg.

How many minimum drives are required to create R5 (RAID 5)?

You need to have at least 3 disk drives to create R5.

Can you name some of the states of RAID array?

There are states of RAID arrays that represent the status of the RAID arrays which are given below:

Online.Degraded.Rebuilding.Failed.

What are the protocols used in physical/datalink and network layer of SAN?

Ethernet.

SCSI.

Fibre Channel.

What is storage virtualization?

Storage virtualization is amalgamation of multiple n/w storage devices into single storage unit.

Describe in brief the composition of FC Frame?

Start of the Frame locator

Frame header (includes destination id and source id, 24 bytes/6 words).Data Payload (encapsulate SCSI instruction can be 0-2112 bytes in length).CRC (error checking, 4 bytes).End of Frame (1 byte).

What is virtualization?

Virtualization is logical representation of physical devices. It is the technique of managing and presenting storage devices and resources functionally, regardless of their physical layout or location. Virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in a storage area network (SAN). The management of storage devices can be tedious and time-consuming. Storage virtualization helps the storage administrator perform the tasks of backup, archiving, and recovery more easily, and in less time, by disguising the actual complexity of the SAN.

What is HA?

HA High Availability is a technology to achieve failover with very less latency. Its a practical requirement of data centers these days when customers expect the servers to be running 24 hours on all 7 days around the whole 365 days a year usually referred as 24x7x365. So to achieve this, a redundant infrastructure is created to make sure if one database server or if one app server fails there is a replica Database or Appserver ready to take-over the operations. End customer never experiences any outage when there is a HA network infrastructure.

Can you name some of the available tape media types?

There are many types of tape media available to back up the data, some of them are:

DLT: Digital Linear Tape technology for tape backup/archive of networks and servers; DLT technology addresses midrange to high-end tape backup requirements.

LTO: Linear Tape Open; a new standard tape format developed by HP, IBM, and Seagate.

AIT: Advanced Intelligent Tape; a helical scan technology developed by Sony for tape backup/archive of networks and servers, specifically addressing midrange to high-end backup requirements.

Can we assign a hot spare to R0 (RAID 0) array?

No, since R0 is not redundant array, failure of any disks results in failure of the entire array so we cannot rebuild the hot spare for the R0 array.

Name the features of SCSI-3 standard?

QAS: Quick arbitration and selection.Domain Validation.CRC: Cyclic redundancy check.

What is Multipath I/O?

Fault tolerant technique where, there is more than one physical path between the CPU in the computer systems and its main storage devices through the buses, controllers, switches and other bridge devices connecting them.

What is disk array?

Set of high performance storage disks that can store several terabytes of data. Single disk array can support multiple points of connection to the network.

What are different types of protocols used in transportation and session layers of SAN?

Fibre Channel Protocol (FCP).

Internet SCSI (iSCSI).

Fibre Channel IP (FCIP).

What is the type of Encoding used in Fibre Channel?

8b/10b, as the encoding technique is able to detect all most all the bit errors

What are the main constrains of SCSI in storage networking?

Deployment distance (max. of 25 mts).

Number of devices that can be interconnected (16).

What is a Fabric?

Interconnection of Fibre Channel Switches.

What are the services provided by Fabric to all the nodes?

1. Fabric Login.2. SNS.3. Fabric Address Notification.4. Registered state change notification.5. Broadcast Servers.

What is the difference between LUN and WWN?

LUN: Unique number that is assigned to each storage device or partition of the storage that the storage can support.

WWN: 64bit address that is hard coded into a fibre channel HBA and this is used to identify individual port (N_Port or F_Port) in the fabric.

What are the different topologies in Fibre Channel?

1. Point-to-Point.2. Arbitrary Loop.3. Switched Fabric Loop.

What are the layers of Fibre Channel Protocol?

1. FC Physical Media.2. FC Encoder and Decoder.3. FC Framing and Flow control.4. FC Common Services.5. FC Upper Level Protocol Mapping.

What is zoning?

Fabric management service that can be used to create logical subsets of devices within a SAN. This enables portioning of resources for management and access control purpose.

What is the purpose of disk array?

Probability of unavailability of data stored on the disk array due to single point failure is totally eliminated.

How does FC Switch maintain the addresses?

FC Switch uses simple name server (SNS) to maintain the mapping table.

What are the two major classification of zoning?

Two types of zoning are:

1. Software Zoning.2. Hardware Zoning.

What are different levels of zoning?

1. Port Level zoning.2. WWN Level zoning.

3. Device Level zoning.4. Protocol Level zoning.5. LUN Level zoning.

What are the 3 prominent characteristics of SAS Protocol?

1. Native Command Queuing (NCQ.)2. Port Multiplier.3. Port Selector.

What are the 5 states of Arbitrary Loop in FC?

1. Loop Initialization.2. Loop Monitoring.3. Loop arbitration.4. Open Loop.5. Close Loop.

What is LUN Masking?

A method used to create an exclusive storage area and access control. And this can be achieved by storage device control program.

What is snapshot?

A snapshot of data object contains an image of data at a particular point of time.

What is hot-swapping?

Devices are allowed to be removed and inserted into a system without turning off the system

Storage interview questions & answers for Series 1

1) What is the differerence b/w SAN and NAS ?

The basic difference between SAN and NAS , SAN is Fabric based and NAS is Ethernet based.SAN - Storage Area NetworkNAS - Network attached Storage

2)What is a typical storage area network consists of - if we consider it for implementation in a small business setup ?If we consider any small buisenss following are essentials componets of SAN

- Fabric Switch- FC Controllers- JBOD's

3)Can you briefly explain each of these Storage area components?Fabric Swictch: It's a device which interconnects multiple network devices .There are swithes starting from 16 port to 32 ports which connect 16 or 32 machine nodes etc.Vendors who manufacture these kind of switches are Brocade, McData.

FC Controllers : These are Data transfer medias they will sit on PCI slots of Server,u can configure Arrays and volumes on it.

JBOD: Just Bunch of Disks is Storage Box,it consists of Enclosure where set of harddrives are hosted in many combinations such SCSI drives,SAS ,FC,SATA.

4)What is the most critical component in SAN ?Each component has its own criticality with respect to buisness needs of a company.

5) Define RAID ? Which one you feel is good choice ?

RAID (Redundant array of Independent Disks) is a technology to achive redundancy with faster I/O.The 123re are Many Levels of RAID to meet different needs of the customer which are : R0,R1,R5,R10,R5.Generally customer choose R5 to achive better redundancy and speed and it is cost effective.

6)How is a SAN managed ?

There are many management softwares used for managing SAN's to name a few

- Santricity- IBM Tivoli Storage Manager.- CA Unicenter.- Veritas Volumemanger.

7) Which one is the Default ID for SCSI HBA ?

Generally the default ID for SCSI HBA is 7.SCSI- Small Computer System InterfaceHBA - Host Bus Adaptor

8) How do you install device drivers for the HBA first time during OS installation ?

In some scenarios you are supposed to install Operating System on the drives connected thru SCSI HBA or SCSI RAID Conrollers,but most of the OS'es will not be updated with drivers for those controllers,that time you need to supply drivers externally,if you are installing windows ,you need to press F6 during the installion of OS and provide the driver disk or CD which came along with HBA.If you are installing linux you need to type "linux dd" for installing any driver.

9) What is Array ?

Array is a group of Independent physical disks to configure any Volumes

or RAID volumes.

10)Can u describe atleast 3 troubleshooting scenarios which you have come across in detail ?

SCENARIO 1:How do you find/debug when there is error while working SCSI devices?

In our daily SAN troubleshooting there are many management and configuration tools we use them to see when there is a failure with target device or initiator device.Some time it is even hard to trouble shoot some of the things such as media errors in the drives, or some of the drives taking long time to spinnup.In such cases these utilities will not come to help.To debug this kind of information most of the controller will be implemented with 3-pin serial debug port. With serial port debug connector cable you can collect the debug information with hyper terminal software.

SCENARIO 2: I am having an issue with a controller its taking lot of time to boot and detect all the drives connected how can I solve this.?

There are many possibilities that might cause this problem. One of the reason might be you are using bad drives that cannot be repaired . In those cases you replace the disks with working ones.

Another reason might be slots you connected your controller to a slot which might not be supported.Try to connect with other types of slots.

One more probable reason is if you have flashed the firmware for different OEMs on the same hardware.To get rid of this the flash utilities will be having option to erase all the previous and EEPROM and boot block entry option. Use that option to rectify the problem.

SCENARIO 3: I am using tape drive series 700X , even the vendor information on the Tape drive says 700X, but the POST information

while booting the server is showing as 500X what could be the problem?

First you should make sure your hardware is of which series , you can find out this in the product website.Generally you can see this because in most of the testing companies they use same hardware to test different series of same hardware type. What they do is they flash the different series firmware. You can always flash back to exact hardware type

Below are the 10 questions asked in an interview with SAN company StorageTek .

1) Which are the SAN topologies?

Answer :SAN can be connected in 3 types which are mentioned below:Point to Point topologyFC Arbitrated Loop ( FC :Fibre Channel )Switched Fabric

2) Which are the 4 types of SAN architecture typesAnswer :Core-edgeFull-MeshPartial-MeshCascade

3) which command is used in linux to know the driver version of any hardware device ?Answer : dmesg

4) How many minimum drives are required to create R5 ( RAID 5) ?

Answer : You need to have at least 3 disk drives to create R5.

5) Can you name some of the states of RAID array ?

Answer : There are states of RAID arrays that represent the status of the

RAID arrays which are given belowonlineDegradedRebuildingFailed

6) Name the features of SCSI-3 standard ?

Answer : QAS: Quick arbitration and selectionDomain ValidationCRC: Cyclic redundancy check

7) Can we assign a hot spare to R0 (RAID 0)array?

Answer :No, since R0 is not redundant array, failure of any disks results in failure of the entire array so we cannot rebuild the hot spare for the R0 array.

8) Can you name some of the available tape media types ?

Answer :There are many types of tape media available to back up the data some of them areDLT :digital linear tape - technology for tape backup/archive of networks and servers; DLT technology addresses midrange to high-end tape backup requirements.LTO :linear tape open; a new standard tape format developed by HP, IBM, and Seagate.AIT :advanced intelligent tape; a helical scan technology developed by Sony for tape backup/archive of networks and servers, specifically addressing midrange to high-end backup requirements.

9) what is HA ?

Answer : HA High Availability is a technology to achive failover with very less latency. Its a practical requirement of data centers these days when customers expect the servers to be running 24 hours on all 7 days around the whole 365 days a year - usually referred as 24x7x365. So to

achieve this a redundant infrastructure is created to make sure if one database server or if one app server fails there is a replica Database or Appserver ready to takeover the operations. End customer never experiences any outage when there is a HA network infrastructure.

10) What is virtualization?

Answer :Virtualization is logical representation of physical devices. It is the technique of managing and presenting storage devices and resources functionally, regardless of their physical layout or location.Virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in a storage area network (SAN). The management of storage devices can be tedious and time-consuming. Storage virtualization helps the storage administrator perform the tasks of backup, archiving, and recovery more easily, and in less time, by disguising the actual complexity of the SAN.Virtualization is a topic of real importance and will be covered in detail in one of our future blogpost

What are the daily tasks of a SAN professional - What are the routine jobs he is responsible for - What happens in a SAN industry engineers' day in office.

Answer :As with any software professional's life the day starts with a brief review of going through the Mails - Since we are dependent on many other teams who are located in different time zones & geos we usually find nearly 50 to 150 new emails in our inbox when we start our day.

We go through all these mails - some of them are very much relevant to our day's tasks like "Storage Product enhancement or development efforts " , " New fixes which will impact our earlier planning" , Lots of organisation wide mails saying who will be our new director or finance manager , Lots of Network or system or UPS outage mails , Lots of mails

about the CR's (Change request or Bugs) which we or one our teammate has logged and what are the latest updates regarding these bugs. The list of mails is endless so we better can have a separate posting for that.

Then based on our mails and our seniors(manager or lead) inputs and also based on our earlier days work we make our small "To Do " list for the day which is some how planned with keeping in mind the "Dreaded Project Deadlines" ( End dates for us to finish the assigned tasks).

An example of our To Do list can be something like :1. Go through the docs about the new features coming in the next release or version of the storage area network product.2. Setup a test environment to reproduce the CR's or bugs logged by customers. ( the end users of our storage products)3. Verify the CR's fixed by dev team ( we logged 10 bugs last week they fixed it 2 days back & delivered the new fix in our latest build of the product yesterday so we need to verify it today ) - We need to verify the fix & say that the fix has resolved the issue also called the product defect or NOT. If the bug is fixed (resolved) we close the CR saying the FIX is FINE(works) else we say the FIX has failed ( the bug still exists & the development team has not fixed it properly)4. Write new test scripts to check the regressions filed by customers -We also do test development ( We develop and script or code the test cases or test scenarios - this involves lot of learning , implementation & improving )5. Setup new 2 Terrabyte disk array & test how well is it working withlatest Vista or latest Suse or RHEL linux.

the list grows along the day & some of them move for next day's ToDo list.

Then we start the actuall work to accomplish what we have put in our ToDO list.We may be working with new release of our SAN product and need to carry out sanity checks on the builds ,creating setups with different hardware and configurations and Operating Systems. We try to replicate

customer network setups as far as possible but a customer like Citibank can have a huge SAN network costing billions of dollars what we can afford to replicate is no where comparable to that. We can say we setup a scaled down SAN network to work in our lab for all our work

CLARRION

Explain Clariion architecture?

The CLARiiON storage system is based on a modular architecture. The first building block of the architecture is the Disk Processor Enclosure, or DPE. The DPE houses the storage Processor(s) and the first Fibre Channel Arbitrated Loop (FC-AL) disks. Disk Array Enclosures (DAEs) are interconnected using Link Control Cards (LCCs).The module architecture allows the customer to add drives as needed to meet capacity requirements. When more capacity is required, additional disk array enclosures (DAE or DAE2) containing disk modules can be easily added. LCC or Link Control Cards are used to connect shelves of disks. In addition, the LCC monitors the FRUs within the shelf and reports status information to the storage processor. The LCC contains bypass circuitry that allows continued operation of the loop in the event of port failure.

Newer CLARiiON arrays have two processors per Storage Processor, and do not use a DPE. Instead, it utilizes an SPE or Storage Processor Enclosure. The SPE does not contain any disk modules, so it must have at least one DAE2 and a maximum of 16 DAE2s. CLARiiON Architecture is based on intelligent Storage Processors that manage physical drives on the back end and service host requests on the front end, be it Fibre Channel or iSCSI protocols. Storage Processors communicate to each other over the CLARiiON Messaging Interface (CMI). Both the front-end connection to the host and the back-end connection to the physical storage is 2Gb Fibre channel.

What are different types of Clariion models?

CX-200,300,300i,400,500,500i,600 and 700

CX3-10, 20, 40 and CX3-80

CX4-120, 240, 480 and CX4-960

AX Series

FC Series

What are the management tools for Clariion?

NaviCli

NaviSphere Manager

EMC Control Center

SymCli

Minimum number of disks required to create RAID 1/0 raid group?

4,6,10

What is Access Logix?

Access Logix provides LUN masking that allows sharing of storage system.

What are the significant features of Access Logix?

LUN masking.

Presents a virtual storage system.

Maps CLARiiON LUNs (FLARE LUNs) to host LUNs.

Manages the Access Control List.

Manages Initiator Registration Records - Access Logix database entries.

Why Access Logix has to be enabled?

If Access Logix is not enabled all LUNs are presented to all storage system ports. Any host that connects to the storage system will then have access to all of the LUNs on that storage system. In environments where multiple hosts attach to the storage system, this will cause problems. Windows systems may attempt to take ownership of LUNs belonging to other Windows systems, and Unix systems may try to mount Windows LUNs, Access Logix solves these problems by performing LUN masking it masks certain LUNs from hosts that are not authorized to see them, and presents those LUNs only to the server(s) which are authorized to see them. In effect, it present a virtual storage system to each host the host sees the equivalent of a storage system dedicated to it alone, with only its own LUNs visible to it.

Another task which Access Logix performs is the mapping of CLARiiON LUNs, often called FLARE LUNs or FLUs, to host LUNs. It will determine which physical addresses, in this case the device numbers, each attached host will use for its LUNs. Note that this feature is configurable by the user through the CLI and the GUI. Access to LUNs is controlled by information stored in the Access Logix database, which is resident in a reserved area of CLARiiON disk - the PSM LUN. The Access Logix software manages this database.When host agents in the CLARiiON environment start up, typically shortly after host boot time, they send initiator information to all storage systems they are connected to. This initiator information is stored in the Access Logix database

How can you check and enable Access Logix?

Right click on Clariion Array select Properties from the drop down menu.

Click on Storage Access Tab

Check whether Access Control Enabled

How many initiators can be connected per port in CX500 CX600?

CX500 64 Initiators/Port

CX600 32 Initiators/Port

What is CMI? Clariion Message Interface?

Storage Processors communicate to each other over the CLARiiON Messaging Interface (CMI).

What is SP Collects and how do you gather SP Collects?

Spcollect is a Storage Processor based perl script which gathers significant information from the Storage Processor and bundles this information for investigation by engineering.

navicli h {ip} spcollect {eng mode password} invoke the spcollects

navicli h {ip} managefiles list to monitor the progress

navicli h {ip} managefiles retrieve file {filename} to transfer spcollect file to management host.

The managefiles command will transfer the data file to the Navisphere CLI directory where the command was invoked.

Explain step by step procedure to assign a LUN to existing Host?

Will check is there any free space is available in existing RAID group as per the required LUN Capacity.

If not available create the new RAID group

Bind the LUN

Will go to the hosts storage group properties and open the LUN tab and add the newly created LUN

Explain step by step procedure for storage provision to the new host?

Installing HBA drivers in new host

Installing NaviAgent

Installing Powerpath if required

Creating Zone, add new zone to zone set, save and enable the zone.

Checking the host connectivity status in the array

Create a new RAID

Bind a LUN (create LUNs as per the host requirement)

Create a metaLUN if required

Create a Storage Group

Add Host and LUN in the storage group properties window

Reboot the host and check the LUN visibility at host-end.

What are pre requisites for LUN migration?

Migration moves data from one LUN to another LUN

Any RAID type to any RAID type, FC to ATA or ATA to FC

Neither LUN may be private LUNs or Hot Spares

Neither LUN may be binding, expanding, or migrating

Either or both may be metaLUNs

Destination LUN may not be in a Stora ge Group

Destination LUN may not be part of SnapView or MirrorView operations

Destination LUN may be larger than Source LUN

How do you create a Meta LUN?

Right Click on LUN > Select Expand > Expand Storage Wizard will appear click on Next > Select the Expansion Type (Stripped or Concatenate) and Click on Next > Confirm the Preserve Data dialog > Select the members (LUN) of Meta and click on Next > Select the User Capacity and click on Next > give the MetaLUN name, Default Owner, Expansion Rate, etc.. and click on Next > Review the Summary and click on Finish

What is the recommended ration of Read and Write cache?

80% Read and 20% Write Cache

How do you troubleshoot if the Hosts are not registering issue?

1. Right click on clariion array and check the connectivity status whether the initiators are showing. If it is showing check whether the initiators are logged in.

2. If it is showing under connectivity status and registered status showing "NO" then you need to install Agent or else you need to register it manually.

3. If it is Registered and not logged in then you need to check the Zoning side and physical connectivity.

4. if the host initiators are not showing under connectivity status at all then you need check the zoning and physical connectivity. If possible remove the zone and create it back. Once you create the zone dont forget to Enable and Save the config. After this just refresh it.

5. Once all these tasks are fine then you can login to Navisphere and update the array once. Update is over then you can go to connectivity status and check

What are the significant features of MetaLUN?

A metaLUN is created by combining LUNs

Dynamically increase LUN capacity

Can be done on-line while host I/O is in progress

A LUN can be expanded to create a metaLUN and a metaLUN can be further

expanded by adding additional LUNs

Striped or concatenated

Data is restriped when a striped metaLUN is created

Appears to host as a single LUN

Added to storage group like any other LUN

Can be used with MirrorView, SnapView, or SAN Copy

Supported only on CX family with Navisphere 6.5+

What are the significant features of FLARE operating systems?

FLARE Operating Environment runs in the CLARiiON Storage Processor. I/O handling, RAID algorithms.

End-to-end data protection.

Cache implementation.

Provisioning and resource allocation.

Memory budgets for caching and for snap sessions, mirrors, clones, copies.

Process Scheduling.

Boot Management.

What are the significant features of Cache Memory?

Cache memory on an SP performs two tasks:

Staging: Temporary buffering of current read and write data.

Always performed on each I/O.

Storage: Repository for frequently accessed data.

Maintaining copies of read and write data.

User must explicitly enable this (for both read and write).

Burst Smoothing - Absorb bursts of writes without becoming disk bound.

Write cache optimization.

Locality - Merge several writes to the same area into a single operation.

Increases write performance.

Immediacy - Satisfy user requests without going to the disks.

Read cache optimization prefetching of data for sequential reads.

What are the significant features of Clariion Event Monitor?

The Event Monitor GUI is integrated with Navisphere Manager.

Event Monitor is part of the Navisphere Agent.

Monitors for user-configurable events.

Reports those events in user-configurable ways.

May launch other utilities/applications.

Can send SNMP traps to Enterprise Management Platforms.

What are the Clariion Operating Layers?

EMC Control Center/ Clariion Based Applications

Navisphere Manager/NaviCli

FLARE Operating Environment

Clariion Hardware

Explain step by step procedure for LUN migration?

Right Click on the LUN and select migrate from the drop down menu.

Select the migration rate and click on OK.

We can check the status from migration tab in the LUN properties page.

What is the process of LUN Migration Operations?

Data is copied from Source LUN to Destination LUN

- Source stays online and accepts I/O

Destination assumes identity of Source when copy completes

- LUN ID, WWN

- Storage Group membership

Source LUN is unbound after copy completes

The migration process is non-disruptive

There may be a performance impact

LUN Migration may be cancelled at any point

- Storage system returns to its previous state

What is Private LUN?

The LUN becomes private LUN when you add it to the reserved LUN pool. Since the LUNs in the reserved LUN pool are private LUNs, they cannot belong to storage groups and a server cannot perform I/O to them.

What is Reserved LUN Pool?

The reserved LUN pool works with replication software, such as SnapView, SAN Copy, and MirrorView/A to store data or information

required to complete a replication task. The reserved LUN pool consists of one or more private LUNs

How do you create a user and assign access rights?

Click on Tools > Click on Security > Click on User management

From the User Management windows Click on Add

Give the user name, Role, access level (Global or Local) and password.

How do you monitor Clariion alerts?

Using Clariion Event Monitor

How the Clariion Event Monitor works?

The Event Monitor GUI is integrated with Manager

Event Monitor is part of the Navisphere Agent

Event Monitor is designed to run in the background, without permanent supervision by the operator

Once Event Monitor is initially configured, there is no further need to run UI

Event Monitor relies on the text file navimon.cfg

Self-documenting text file included in Interface Kit

Does not require Event Monitor UI

Monitor Agents run on one or more hosts (or SPs) and watch over the storage systems

When an event is detected, the agent notifies the user As defined by navimon.cfg

Can send SNMP traps to Enterprise Management Platforms.

What are Vault drives and how much capacity they use?

Clariion Platform_____:Vault Drivers____:Vault overhead per drive

CX____________________:0-4______________:6.22 GB

CX3___________________:0-4______________:33 GB

CX4___________________:0-4______________:62 GB

AX4-5_________________:0-3______________:17.4 GB

Vault Drives:

All Clariions have Vault Drives. They are the first five (5) disks in all Clariions. Disks 0_0_0 through 0_0_4. The Vault drives on the Clariion are going to contain some internal information that is pre-configured before you start putting data on the Clariion. Vault Drives contains Vault area, PSM Lun, Flare database Lun and Operating System.

The Vault:

The vault is a save area across the first five disks to store write cache from the Storage Processors in the event of a Power Failure to the Clariion, or a Storage Processor Failure.

The PSM Lun:

The Persistent Storage Manager Lun stores the configuration of the Clariion. Such as Disks, Raid Groups, Luns, Access Logix information, SnapView configuration, MirrorView and SanCopy configuration as well.

Flare Database LUN:

The Flare Database LUN will contain the Flare Code that is running on the Clariion. I like to say that it is the application that runs on the Storage Processors that allows the SPs to create the Raid Groups, Bind the LUNs, setup Access Logix, SnapView, MirrorView, SanCopy, etc

Operating System:

The Operating System of the Storage Processors is stored to the first five drives of the Clariion.

How do you create a user and assign access rights?

Click on Tools > Click on Security > Click on User management

From the User Management windows Click on Add

Give the user name, Role, access level (Global or Local) and password

What is Private LUN?

The LUN becomes private LUN when you add it to the reserved LUN pool. Since the LUNs in the reserved LUN pool are private LUNs, they cannot belong to storage groups and a server cannot perform I/O to them.

What is Reserved LUN Pool?

The reserved LUN pool works with replication software, such as SnapView, SAN Copy, and MirrorView/A to store data or information required to complete a replication task. The reserved LUN pool consists of one or more private LUNs.

What are the significant features of Cache Memory?

Cache memory on an SP performs two tasks:

Staging: Temporary buffering of current read and write data.

Always performed on each I/O.

Storage: Repository for frequently accessed data.

Maintaining copies of read and write data.

User must explicitly enable this (for both read and write).

Burst Smoothing - Absorb bursts of writes without becoming disk bound.

Write cache optimization.

Locality - Merge several writes to the same area into a single operation.

Increases write performance.

Immediacy - Satisfy user requests without going to the disks.

Read cache optimization prefetching of data for sequential reads.

SYMMETRIX

Can you explain about DMX Architecture?

The Symmetrix DMX features a high-performance, Direct Matrix Architecture (DMX) supporting up to 128 point-to-point serial

connections. Symmetrix DMX technology is distributed across all channel directors, disk directors, and global memory directors in symmetrix DMX systems.

Can you briefly explain about symmetrix series products?

Symmetrix 8000/4 was the first symmetrix to introduce a dual bus arcitecture, providing redundancy in the path to memory.

Symmetrix DMX800 is an incrementally scalable, high-end storage array which features modular disk array enclosures.

Symmetrix Direct Matrix Architecture is storage array technology that employs a matrix of dedicated serial point-to-point connections instead of traditional buses or switches.

Symmetrix DMX2 is a channel director specification for the DMX with faster processors and newer components.

Symmetrix DMX-3 and DMX-4 are the latest technology using redundant global memory and largest capacity.

Can you explain Enginuity release code 5773.79.58?

57 represents the DMX3/4 Hardware 73 represents the microcode family 79 represents the field release level to the microcode 58 represents the field release to the service processor code

52 =Symm4, 55 =Symm5, 56 =DMX/DMX2, 57 =DMX3/4, 58 =VMAX.

How many Cache directors, Front-end directors and Back-end directors we can use in DMX-4?

Cache Directors = 4 Min to 8 Max. Front-end Directors = up to 12 max. Back-end Directors = 6 Min to 8 Max.

What are the different types of Front-end directors and the purposeof each one?

ESCON (EA) : for mainframe attachment and SRDF family links FICON (EF) : provides the industrys highest performance connectivity Option for the mainframe.

Fibre (FA/DA) : Connectivity option for open systems direct and SAN Attachment, and can be used for SRDF family remote Replication links. iSCSI (SE) : Provides the industrys first high-end Iscsi Implementation. GigE (RE) : for SRDF family replication with compression support.

Explain Rule 17 in DMX?

Possible answers: Rule of 17 ensured that FAs being used for host connectivity were in different power zones.

The rule of 17 is simply a way to make sure that the paths you connect your host to are not running on the same director, but one physically far away from it.

The original Rule of 17 was put into place to ensure that there was a path on each bus (odd and even).The bus architecture went away in DMX-1 ( Symm6). But we had 2 power zones; one zone for directors 1-8, and another zone for directors 9-16. So the Rule of 17 still had value.

but DIR 3 (odd) and DIR 4 (even) reside on different buses yet in the same power zone, so even if you had your host connected to 3 and 4 ..if that power zone went down ..Your hosts went down

What are the Management Tools for DMX?

Symcli (Symmetrix Command Line Interface) SMC (Symmetrix Management Console) ECC (EMC Control Center)

What are the Enginuity Operational Layes?

Symmetrix Based Application Host Based Symmetrix Application Independent Software vendor application EMC Solutions Enabler API Symmetrix Enginuity Operating Environment Functions Symmetrix Hardware

What are the major components of System Bay and Storage Bay in DMX?

System Bay Components: Either six or eight disk directors and up to 12 channel directors (Combined total = 16). From four to eight global memory directors.Up to eight power supplies, each of having a dedicated Battery Back Up(BBU) 1U service processor with KVM (keyboard, video screen and mouse) and dedicated UPS. Three cooling fan assemblies (each containing 3 fans).

Storage Bay Components: 120 or 240 disk drives per storage bay Each Drive Enclosure (DE) includes: Two link control cards (LCC). Redundant power supplies with BBUs to provide standby power. The DMX-4 storage bay has 2N power zones with independent power cables, each zone capable of powering the fully configured storage bay. The storage bay can be populated with various combinations of currently available DMX one-inch low-profile 4 Gb/s Fibre Channel disk drives available in: 73 GB, 146 GB, 300 GB, and 400 GB Fibre Channel drives 73 GB and 146 GB Flash drives 500 GB and 1 TB SATA II disk drives

Can you explain about Read Hit, Read Miss and Fast Write and Delayed Write?

Read Hit: In a read hit operation, the requested data resides in global memory. The channel director transfers the requested data through the channel interface to the host and updates the global memory directory. Since the data is in global memory, there are no mechanical delays due to seek and latency.

Read Miss: In a read miss operation, the requested data is not in global memory and must be retrieved from a disk device. While the channel director creates space in the global memory, the disk director reads the data from the disk device. The disk director stores the data in global memory and updates the directory table. The channel director then reconnects with the host and transfers the data. because the data is not in global memory, the symmetrix system must search for data on the disk and then transfer it to the channel adding seek and latency times to

the operation.

Fast Write A fast write occurs when the percentage of modified data in global memory is less than the fast write threshold. On a host write command, the channel director places the incoming blocks directly into global memory. For fast write operations, the channel director stores the data in global memory and sends a channel end and device end to the host computer. The disk director then asynchronously de-stages the data from global memory to the disk device.

Delayed Fast Write: A delayed fast write occurs only when the fast write threshold has been exceeded. That is the percentage of global memory containing modified data is higher than the fast write threshold. If this situation occurs, the symmetrix system disconnects the channel directors from the channels. The disk director then de-stages the data to disk. When sufficient global memory space is available. The channel directors reconnect to their channels and process the fast I/O requires as a fast write. The symmectrix system continues to process read operations during delayed fast writes with sufficient global memory present, this type of global memory operation rarely occurs.

How do you calculate number of cylinders for 120 GB LUN?

Maximum device sizes by Enginuity version Enginuity version:__________:MBs:_______:CYLs:______:GBs Enginuity 5874:_____________:245760:____:262668:____:240 Enginuity 5773 and earlier:_:61425:_____:65520:_____:59

Since DMX-4 supports maximum of 60GB hyper size, we have to create two hypers and form a Meta devices as 120GB LUN. To calculate cylinders for 60GB LUN use the below formula Cylinders = 60GB/15 tracks* 8 sectors* 16 blocks * 512 bytes Cylinders = 60000000000/15*8*16*512 Cylinders = 60000000000/983040 Cylinders = 61035 cyl

To calculate the number of cylinders (for pre-Symmetrix DMX), use either of the following: blocks 960 or (size in megabytes) x 2.1333

To calculate the number of cylinders (for Symmetrix DMX and Symmetrix V-Max arrays), use the following: 1 cylinder = 15 tracks; each track is 64 KB, 15 x 64 tracks = .937 MB for each cylinder

What is the maximum hyper size in DMX-4?

Maximum Cylinders = 65520 Maximum Capacity = 59GB or 61425 MB

How many hypers can create in a Single disk in DMX4?

255 hypers per disk.

How many members can contain in one Meta?

1 Meta head + 255 members

What is Dynamic LUN addressing?

This feature will automatically selects and assigns the LUN IDs to the devices while device mapping to the port Instead of manually assigning address to the device while mapping

How do you add a new member to the existing Meta?

add dev XXXX to meta XXXX, protect_data=TRUE, bcv_meta_head=XXXX;

or for multiple ranges:add dev XXX1:XXX6 to meta XXXX, protect_data=TRUE, bcv_meta_head=XXXX;

What is stripping and what is Concatenating?

Stripped Meta Devices: Meta device addressing by striping divides each Meta member device into a series of stripes, addressing a stripe from each device before advancing to the next stripe on the first device. When writing to a striped volume, equal size stripes of data from each participating drive are written alternately to each member of the set.

Concatenated Meta Devices: Concatenated devices are volume sets that are organized with the first byte of data at the beginning of the first device. Addressing continues to the end of the first device before any data on the next device is referenced. When writing to a concatenated device, the first meta device member receives all the data until it is full, and then data is directed to the next member and so on

What are the DMX-4 supported disk types, no. of disks and maximum capacity?

FC drives, iSCSI drives and Flash drives 15 drives per DAE 120 drivers per Cage 240 drives per Storage Bay 2400 drives per array If total of 10 storage bays connected Maximum storage capacity is 1 PB.

Briefly explain the DMX-4 supported Device types?

Standard Devices: A Symmetrix device configured for normal Symmetrix operation under a desired protection method (such as RAID-1,RAID-S, and SRDF).

Gatekeeper Devices: SCSI commands executed by SYMAPI are transferred to the Symmetrix array via a Symmetrix device that is designated as a Gatekeeper device. The gatekeeper allows you to retrieve configuration and status information from the Symmetrix array without interfering with normal device I/O operations.

Meta Devices: Allow individual devices to be concatenated to create larger devices.

BCV Devices: Specialized devices used to create a local copy of data contained in a standard Symmetrix device, which can be used for backup, restore, decision support, and application testing.

SRDF Devices (R1, R2 and R21) Devices configured as RDF1 or RDF2 to support SRDF operations. R1 is source device for SRDF operations R2 is target device for SRDF operations R21 is used for multi hop SRDF operations

Virtual Devices: A host-accessible device containing track-level location information (pointers), which indicates where the copy session data is located in the physical storage. Device copies use virtual devices to support TimeFinder/Snap operations. Virtual devices consume minimal physical disk storage, as they store only the address pointers to the data stored on the source device or a pool of save devices.,

Save Devices: Special devices (not mapped to the host) that provide

physical storage space for pre-update images or changed tracks during a virtual copy session of TimeFinder/Snap operations.

Device Masking (VCM)Devices: Symmetrix devices that have been masked for visibility to certain hosts. The device masking database (VCMDB) holds device masking records and typically resides on a 24 or 48 cylinder disk device..

DRV Devices: A non-user-addressable Symmetrix device used by the Symmetrix Optimizer to temporarily hold user data while reorganization of the devices is being executed. Typically, it is used by the Optimizer in logical volume swapping operations.

What is Vault drives and Hot Spare?

Vault Drivers: At the time of emergency shutdown of an Array, what ever the data in cache memory will be destaged/saved on temporary drives called vault drives

Hot Spare: At the time of physical drive failure hot spare drives will take place

What is Preview, Prepare and Commit while using Symconfigure command?

The preview argument verifies the syntax and correctness of each individual change defined, and then terminates the session without change execution.

The prepare argument performs the preview checks and also verifies the appropriateness of the resulting configuration definition against the current state of the Symmetrix array; the argument then terminates the session without change execution

The commit argument completes all stages and executes the changes inthe specified Symmetrix array

What are the possible device service states and device status states?

Device Service States : Normal, Failed and Degraded Device Status States : Ready, Not Ready and Write Disable.

How do you reserve the devices?

symconfigure -sid XXXX -f createdev.cmd -expire expiration date-owner myself -comment "this devices are reserved for SRDF activity" reserve

How do you create the Disk Groups

We can not create Disk Groups, It should be done by changing BIN file by CE. We can rename the existing disk groups. Example: symconfigure -sid 207 -cmd set disk_group 4 disk_group_name = flash_dsks; -v -nop commit

How do you check the free space by Disk group and Array as whole?

By Disk Group : Symdisk -sid XXXX list -by_diskgroup Array as whole : Symconfigure -sid XXXX list -freespace

How do you check the total assigned devices to a particular Host?

Symmaskdb -sid XXXX list devs -wwn "host hba wwn"

How do you check the total allocated storage of a particular Host?

symmaskdb -sid XXXX list capacity -Host hostname

What is pre check list to assign storage to the host?

Verify the available free space in the symmetrix array symconfigure -sid SymmID [-v | -freespace [-units cylinders | MB]] list symdisk -sid "SymID" list -disk_group "GroupNumber"

Verify the Symmetrix status Symconfigure -sid "SymID" verify

If any hung activities found abort symconfigure -sid "SymID" abort

Explain step by step procedure to provide storage to the Host?

1. Creating STD device 2. Meta Device Creation 3. Mapping 4. Masking

Example: Create a commandfile with the following entry to create hypers.Create dev count=8, size=12394, emulation=FBA, config=2-way-mir, disk_group=2;

Execute the command file using symconfigure command with preview,prepare and commit options. Symconfigure -sid "SymID" -f Commandfile.cmd -v -noprompt commit

Verify the newly created devices symdev -sid "SymID" list -noport

Create a commandfile with following entry to form metas and devices to the meta head. Form meta from dev 26CA, config=striped, stripe_size=1920; add dev 26CB:26E4 to meta 26ca;

Execute the command file using symconfigure command with preview, prepare and commit options. symconfigure -sid "SymID" -f Commandfile.txt -v -noprompt commit

Verify the newly created meta devices symdev -sid "SymID" list -noport

Find the host connected Director and Port details symcfg -sid 4282 list -connections

Find the available addresses on that port symcfg -sid "SymID" list -address -available -dir 7d -p 0

Create a commandfile with the following entry to map the device to the FA port map dev 26ca to dir 7d:0, lun=036;

Execute the commandfile using symconfigure with the preview, prepare and commit options. Symconfigure -sid 4282 -f Commandfile.txt -v -noprompt commit

Mask the devices to the host HBA and refresh the sym configuration symmaskdb -sid "SymID" -wwn 10000000c93f62cf -dir 7d -p 0 add devs 26ca -nop Symmask -sid "SymiD" -refresh

Rescan the disks and refresh the powerpath or reboot the server to get the assigned devices at host-end

How do you check particular device geometry?

symdev -sid XXXX show dev 002C

How do you check the particular device is connected to which Host?

symmaskdb -sid XXXX list assignment -dev 002c

What are the steps for storage reclamation?

Unmasking Write Disable Un-mapping Dissolve meta Deleting hypers

1. Unmasking devices from the host symmaskdb -sid 4282 -wwn 10000000c93f62cf -dir 7d -p 0 remove devs 26ca

2. Refresh the Symmetrix Array Symmask -sid 4282 -refresh

3. Write Disable the devices before unmapping from the Director port symdev -sid 4282 write_disable 26ca -sa 7d -p 0 -noprompt

4. Create a cmd/txt file Unmap dev 26ca from dir all:all;

5. Perform preview operation using symconfigure command Symconfigure -sid 4282 -f unmap.txt -v -nop preview

6. Perform prepare operation using symconfigure command Symconfigure -sid 4282 -f unmap.txt -v -nop prepare

7. Perform Commit operation using symconfigure command Symconfigure -sid 4282 -f unmap.txt -v -nop commit

8. Verify that the device has been unmapped Symdev -sid 4282 list -noport

9. To Dissolve meta, create a cmd/txt file Dissolve meta dev 26ca;

10. Perform preview operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop preview

11. Perform prepare operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop prepare

12. Perform Commit operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop commit

13. Verify that the meta has been Dissoved. Symdev -sid 4282 list -noport

14. To delete the hypers create a cmd/txt file. Delete dev 26ca;

15. Perform preview operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop preview

16. Perform prepare operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop prepare

17. Perform Commit operation using symconfigure command Symconfigure -sid 4282 -f dissolve.txt -v -nop commit

18. Verify that Hypers have been deleted. Symdev -sid 4282 list -noport

How many mirror positions RAID-1 and RAID-5 will occupy?

RAID-1 occupies 2 mirror positions RAID-5 occupies 2 mirror positions

How do you convert the concatenating meta device to stripped meta?

convert meta XXXX, config=striped, stripe_size=1920, protect_data=TRUE, bcv_meta_head=XXXX;

Host is unable to see the storage, how do you troubleshoot?

Check that the host is logged in to the Array Check that the cable connectivity status by logging in to the host Check that the HBA drivers are properly configured Check the Zoning table by logging in to the switch Check that the devices status in Array Check the VCMDB for masking information, etc..

What is Thin Provisioning?

Thin provisioning is a method of optimizing the efficiency with which the available space is utilized in storage area networks. Thin provisioning operates by allocating disk space in a flexible manner among multiple users, based on the minimum space required by each user at any given time

How do you create thin pools and thin devices?

Creating Thin Pools Creating Data devs and added these Data devs to Thin Pools Creating TDEVs and bind these TDEVs to Thin Pool Assign TDEVs to host.

Explain step by step procedure to setup new host?

Let us assume cable connectivity is done properly Install HBA drivers in host. Install Power path if required. Check that the HBA ports are showing online Create zoning at switch end. Check that this host is logged in to the Storage array Create LUN/hypers in storage array Form meta devices if required Map the devices to the FA port. Mask the devices to the host hba (wwn). Refresh the Array to affect the changes

How do you check the failed components in Symmetrix Array?

Symcfg -sid 150 list -env_data -service_state failed

How do you check the failed disks in the Symmetrix Array?

Symdisk -sid XXXX list -failed

What is the purpose of Gate Keeper device?

Low-level I/O commands executed using SYMCLI are routed to the Symmetrix array by a Symmetrix storage device that is specified as a gatekeeper. The gatekeeper device allows SYMCLI commands to retrieve configuration and status information from the Symmetrix array without interfering with normal Symmetrix operations. The gatekeeper must be accessible from the host where the commands are being executed.

How many gate keeper devices are required per Array?

It depends on the Symmetrix management applications using in management servers, As per EMC recommendations 6 gatekeepers are required per management host using symcli

How to list hosts and their EMC registered software, using Solutions Enabler?

Symcfg -sid XXXX list -applications

What is VCMDB and how do you take the backup?

The device masking database (VCMDB) holds device masking records and typically resides on a 24 or 48 cylinder disk device.. Symmaskdb -sid XXXX backup -f filename

How do you list the Hosts which are connected to particular director port?

Symmaskdb -sid XXXX list database -dir XX -p X

How do you check the number of storage bays connected to the system bay and number of disks in each storage bay?

Symcfg -sid XXXX list -env_data

How do you check the number of storage bays connected to the system bay and number of disks in each storage bay?

Symcfg -sid XXXX list -env_data

How do check the devices which are not mapped and masked?

Symdev -sid 4282 list dev -noport

How do you check the devices which are mapped to FA but not masked to any host?

Symmaskdb -sid 123 list no_assignment -dir ALL -p ALL

How do you check the login hosts in the Symmetrix Array?

Symmask -sid 4282 list logins

How to display and set the Symmetrix metrics?

Symcfg -sid XXXX -SA all list -v Set Symmetrix MatricName=MatricValue

How do you check the configured environmental variables?

Symcli -def

Can windows, Linux, Solaris share the same FA in DMX?

Yes, if they share the same port flags

What are the Symmetrix External locks and how to check and release?

Symmetrix external locks are used by SYMAPI (locks 0 to 15) and also for applications assigned by EMC (>15) to lock access to the entire Symmetrix arrayduring critical operations

We can check the external locks by giving the below command symcfg -sid XXXX list -lockn

We can check the external locks by giving the below command symcfg release -sid -lockn 15 -force

How to monitor performance of EMC Symmetrix?

Using Performance Monitoring feature in EMC Control Center Using SYMSTAT symcli command

How do you check the cache activity of front-end directory?

symstat -sid 4282 -type cache -i 5 -c 4 -sa all

How do you check the I/O requests and throughput of selected disk?

Symstat -sid 4282 -type disk -i 5 -c 3 -disk 2a,C,5

What are the available performance types in SYMSTAT command?

REQUESTS: Reports I/O requests and throughput for selected devices, directors, or SRDF/A sessions. (This is the default type; if no type is specified REQUESTS is used.) BACKEND: Reports back-end I/O requests and throughput for selected devices. PORT: Reports performance statistics for a director port. ISCSI Report Gig-E network statistics. CACHE: Reports cache activity for selected front-end or remote link directors, or SRDF/A sessions. MEMIO: Reports cache memory to disk activity for selected devices. PATH Report R-Copy path information for nonincremental sessions. Symmetrix arrays that have all or some incremental sessions will report an error. CYCLE: Report cycle summary information for SRDF-A sessions. DISK: Reports back-end I/O requests and throughput for selected disks. PREFETCH: Reports track prefetch disk activity for selected back-end directors only.DMSP Reports dynamic mirroring service policy (DMSP) statistics for the selected device(s). RDF: Reports SRDF statistics from the perspective of RA groups,devices, or directors.

What is symmetrix optimizer and how it works?

Symmetrix Optimizer improves array performance by continuously monitoring access patterns and migrating devices (Symmetrix logical volumes) to achieve balance across the disks in the array Step 1: Symmetrix Optimizer builds a database of device activity statistics on the Symmetrix back-end.

Step 2: Using the statistical data collected, configuration information, and the user-defined parameters, the Optimizer algorithm identifies busy and idle devicesand their locations on the physical drives. The algorithm tries to minimize average disk service time by balancing I/O activity across physical disks. Optimizer determines which disks require balancing by locating busy devices close to each other on the same disk, and/or by locating busy devices on faster disks or faster areas of the disks. Optimizer takes into account the speed of the disk, the disk geometry, and the actuator speed to determine faster disks.

Step 3: Once a solution for load balancing has been developed, the next phase is to carry out the Symmetrix device swaps. This is done using established TimeFinder technology, which maintains data protection and availability. we can specify whether swaps should occur in a completely automated fashion, or if the device swaps require user approval before the action is taken.

Step 4: Once a swap function completes, Symmetrix Optimizer continues data analysis for the next swap.

What is Symmetrix QoS and how it works?

Quality of Service (QoS) allows more flexibi