EqualLogic High Level Design Document For CustomerX

EqualLogic High Level Design Document For CustomerX

Date:

Author:

EqualLogic Proposal To CustomerX of 19

Contents

Current Situation...................................................................................................................................3EqualLogic Storage Solution – Overview...............................................................................................3EqualLogic Proposal...............................................................................................................................4

Proposed Hardware...........................................................................................................................4Network Connectivity / IP SAN Performance.....................................................................................5Best Practice For Using Exchange With EqualLogic............................................................................8

Memory Configuration..................................................................................................................8Volume Configuration....................................................................................................................8Exchange Startup...........................................................................................................................9EqualLogic Performance Advantage On Exchange.........................................................................9

Best Practice For Using SQL With EqualLogic.....................................................................................9Memory Configuration................................................................................................................10Volume Configuration..................................................................................................................10

Using Backup Exec With EqualLogic.................................................................................................11BackupExec Configurations..........................................................................................................11Using Snapshots To Improve Backups.........................................................................................13Local Snapshots...........................................................................................................................13SAN Snapshots.............................................................................................................................14VSS (Microsoft Volume Shadow Copy Services) Snapshots And Backup......................................15

Replication Capabilities With EqualLogic.........................................................................................16Recovering Volume Data From Replicas......................................................................................18

Summary.............................................................................................................................................19


Current SituationCustomerX’s current environment is mostly direct attached storage or internal disk, with the exception of Exchange which is on an HP MSA1000.In Exchange there are roughly 900 mailboxes with a mailbox limit of 1GB and on average the Exchange usage is considered medium to heavy.CustomerX are embarking on a new document management project based around Interwoven, for this they are looking to consolidate their disparate storage estate.There is also a need for offsite disaster recovery, the link between sites is 100Mb and is also used for user traffic such as Outlook, shares etc.Currently under consideration is the use of VMware for the Interwoven apps servers.The storage estate today is roughly 3TB in total, but the scope will be for 6TB at each site.The hardware needs to be live by Sept 2007.

EqualLogic Storage Solution – OverviewThe foundation of an EqualLogic storage solution is a PS Series group: an iSCSI SAN comprised of one or more PS Series storage arrays (“members” in EqualLogic terminology) connected to an IP network and managed as a single system.

Each array has fully redundant hardware and up to three active network connections for maximum bandwidth. Integrated virtualization firmware provides:

Seamless scalability Automatic RAID configuration and spare disk configuration Automatic network, performance, and capacity load balancing

In a single-member group, data is automatically spread across the array disks. Add more arrays to the group to expand SAN capacity and increase performance—with no disruption to users. Management overhead stays the same, regardless of SAN size.

After an array is added to a group and you choose a RAID level for the new member, the disks are automatically configured, and the space is immediately available for use. Data is spread across group members and automatically load-balanced as needed, based on capacity and performance metrics.

To access the storage space in a group, use the Group Manager graphical or command line user interface to create volumes, each of which has a size, access controls, and other attributes. A volume can be spread across multiple disks and is seen on the network as an iSCSI target.

Optionally, you can use thin provisioning to improve storage resource utilization by logically over-allocating SAN volumes. Thin provisioning enables you to satisfy current and future storage needs and eliminates the difficulty of adding storage to operating systems or applications that do not support online expansion.

A host needs only an industry-standard iSCSI initiator to access a volume in a group. Most major operating systems support an iSCSI initiator (in the form of an iSCSI driver or a host bus adapter), with a range of price and performance options. Once connected, a volume appears as a regular disk that can be formatted with the operating system’s normal utilities. Even as members are added and removed from the group, volumes continue to be accessible through the same iSCSI targets; no host modifications are necessary.

In a group, you can place all the members and volumes in a single storage pool. Or, if you have multiple members, you can create additional pools and assign members and volumes to different


pools. Pools allow you to organize storage according to usage, providing more control over resource allocation, while maintaining a single system management view. You retain the advantages of storage consolidation while gaining the ability to easily segregate workloads.

Hardware: Dual hot-swappable controllers each with dual-core 64-bit RISC processor 2 GB memory, 72 hour battery back up Dual hot-swappable power supplies and fans 6 Gigabit Ethernet ports for iSCSI connectivity; 3 live, 3 standby (a total of 3Gb bandwidth

per array)Software (all the below included at no extra cost):

Wizard driven setup manager Storage Virtualization Heterogeneous OS Support Volume Snapshot – (Up to 512 per Volume, Read-only and Read/Write, Scheduler) Instant Restore from Snapshot Volume cloning Multi-way replication Automatic volume management Automatic load balancing Automatic optimisation Automatic storage tiering PS Group Manager RAID 5, 10 or 50 with hot sparing Ability to downgrade RAID levels on the fly with no interruption (thereby providing extra

capacity at no extra cost) Auto-snapshot Manager Multi-Path IO support Thin Provisioning Roles Based Admin

EqualLogic ProposalProposed HardwareSiteA:1 x PS3900XV (16 x SAS 15k rpm 300GB drives, 1.8TB useable in RAID10)1 x PS400E (14 x SATA 7200 rpm 750GB drives, 4.0TB useable in RAID10)

Having two arrays at siteA will provide a tiered storage environment – frequently accessed data or application data that needs high levels of performance can be hosted on the PS3900XV and less frequently accessed data can be hosted on the PS400E; this tiering can be automated (data will be moved between arrays based on IO profiling and access patterns) or can be set on a per-volume basis. Both arrays are configured at RAID 10 (mirrored stripes) which gives best performance at the expense of capacity; note that EqualLogic arrays can be reconfigured from RAID10 to RAID50 on the fly (no interruption to IO) thereby providing instant extra capacity at no extra cost, over time you will be able to monitor utilisation rates of the arrays and it may be that RAID50 will provide sufficient performance.

SiteB:1 x PS400E (14 x SATA 7200 rpm 750GB drives, 6.6TB useable in RAID50)


For siteB the PS400E will be in RAID50 configuration (all data striped across two RAID5 sets), thereby giving maximum capacity, yet still giving good performance. It is worth noting that in our experience we have often seen SATA based arrays at RAID50 outperform DAS by around 20%. Most customers typically have a lower specification array at the DR site as it should only be used in extreme circumstances and for a limited period until the main production site resumes normal operation.

Network Connectivity / IP SAN PerformanceThe networking requirements for group members are described in the table below.

Networking Requirements Requirement Description Use the network cable that is right for your type of network.

For copper-based networks, use Category 5E or Category 6 cables with RJ45 connectors. You can also use Category 5 cables if they adhere to the TIA/EIA TSB95 standard. For fiber optic networks, use cables with LC connectors. Fiber optic networks also require small form factor pluggable (SFP) connectors, which can be obtained from EqualLogic.

Each array must have at least one network connection.

An array must have at least one active network connection and can have a maximum of three.

Each array must have network access to the group IP address.

An array must have at least one network interface configured on the same subnet as the group IP address.

In a single-subnet group, you must have connectivity between switches.

In a single-subnet group in which the arrays’ configured network interfaces are connected to multiple switches, there must be network connectivity between the switches.

For optimal performance and availability, follow the recommendations in the table shown next. The following sections provide background information on some of the recommendations.

Networking Recommendations Recommendation Description Configure multiple network connections on an array.

Connecting multiple network interfaces on an array and assigning each interface an IP address and netmask improves performance and availability. Connect the cables to different switches, if possible.

In a multi-subnet group, ensure access to the group IP address.

In a multi-subnet group, the arrays’ configured network interfaces should be able to access the subnet on which the group IP address resides.

Use a switched, Gigabit Ethernet network. For the best performance, you should connect arrays and hosts to a switched network and make sure that all network connections between hosts and arrays are Gigabit Ethernet. An array can operate at 10 and 100 Megabits, but performance will be


significantly degraded. Use redundant network paths between hosts and arrays.

A multipathing solution helps to ensure that no single point of failure exists between hosts and arrays.

For replication, use a reliable, adequately sized network link.

For effective and predictable replication, be sure that the network link between the primary and secondary groups is reliable and provides sufficient bandwidth for copying data.

Do not use STP on switch ports that connect end nodes.

It is recommended that you do not use Spanning-Tree (STP) on switch ports that connect end nodes (iSCSI initiators or storage array network interfaces). However, if you want to use STP or RSTP (preferable to STP), you should enable the port settings available on some switches that let the port immediately transition into STP forwarding state upon link up (for example, Cisco’s PortFast option). This functionality can reduce network interruptions that occur when devices restart, and should only be enabled on switch ports that connect end nodes. Note: The use of Spanning-Tree for a single-cable connection between switches is encouraged, as is the use of trunking for multi-cable connections between switches.

Use Flow Control on switches and NICs. It is recommended that you enable Flow Control on each switch port that handles iSCSI traffic. If your server is using a software iSCSI initiator and NIC combination to handle iSCSI traffic, you must also enable Flow Control on the NICs to obtain any performance benefit. PS Series storage arrays will correctly respond to Flow Control.

Disable unicast storm control on switches that provide this functionality.

It is recommended that you disable unicast storm control on each switch that handles iSCSI traffic. However, the use of broadcast and multicast storm control is encouraged on switches. Not all switches provide unicast storm control functionality.

Use Jumbo Frames on switches and NICs. Enable Jumbo Frames on each switch that handles iSCSI traffic. If your server is using a software iSCSI initiator and NIC combination, you must also enable Jumbo Frames on the NICs that handle iSCSI traffic to obtain any performance benefit and ensure consistent behavior.

Use VLANs, or use dedicated switches for the IP SAN

Configure VLANs on switches to separate iSCSI traffic from other network traffic.


Alternatively create a completely separate IP SAN environment.

The following figure shows how you can increase network availability and performance in a dual control module array by adding network connections. Note that you can connect all six network interface ports to the network for guaranteed full bandwidth.

Dual Control Module Array Network Connections

The diagram below shows the recommended configuration for a SATA based array.

Best Practice For Using Exchange With EqualLogicTo get the maximum benefits from Exchange and PS Series storage, you should adhere to the best practices for Exchange Server 2003, as outlined by Microsoft and industry experts. In addition, this section describes requirements and recommendations for deploying Exchange Server 2003 with PS


Series storage, including best practices for performance, reliability, scalability, flexibility, and recoverability.

Memory ConfigurationMemory configuration can affect the storage I/O load and performance. An Exchange server configured without sufficient memory will generate heavier I/O loads to storage; alternately, configuring sufficient memory will make your Exchange installation more efficient in its use of storage resources. By making your server as tuned and efficient as possible, you can get the maximum benefit from using PS Series storage. For Exchange Server 2003 memory optimization details, see the following Microsoft Knowledge Base article, titled How to optimize memory usage in Exchange Server 2003: http://support.microsoft.com/?kbid=815372

There are various ways to optimize Exchange server memory resources. For a detailed article on how to determine if you need more memory in your Exchange server and how to diagnose memory utilization issues in Exchange 2003, see the following Microsoft TechCenter article, titled Troubleshooting Exchange Server 2003 Performance: http://www.microsoft.com/technet/prodtechnol/exchange/2003/library/e2k3perf.mspx

For additional memory performance you may need to alter some entries in boot.ini, as well as modifying specific registry keys.

Volume ConfigurationExchange server has a number of different files with different functions that make up the storage installation. For example, each Exchange server includes the following:

Private mail store files, also referred to as the Jet databases, (priv.edb, priv.stm) Public mail store database files (pub.edb, pub.stm) Exchange transaction logs (*.log)

For an Exchange installation, it is recommended that you do the following: Create two volumes in the PS Series SAN for each Storage Group, one volume for the

databases and one volume for the logs. If you are using multiple mail stores in a Storage Group, put the mail stores on the same

volume.

Note: Although you can put each mail store on its own volume, there is no real management advantage, because the log volume is common for all mail stores within an Exchange Storage Group, and backups of the database and the logs should occur at the same time, preferably using VSS. When using a PS Series group, there is no performance advantage either to separating mail stores, since I/O is automatically load balanced across the volumes.

If using SAN boot for the Exchange servers, you must also set up the volumes for this configuration.

Exchange StartupWhen using PS Series volumes connected through the Microsoft software iSCSI initiator to hold some or all of the files associated with an Exchange Server information store, you must prevent the Exchange Server from attempting to start before the iSCSI volumes are online. Therefore, you must add a dependency to the Registry information for the corresponding services to delay their startup until after the iSCSI service has started. Refer to Microsoft Knowledge Base article 193888, "How to Delay Loading of Specific Services," for general information on this topic.


http://www.microsoft.com/technet/prodtechnol/exchange/2003/library/e2k3perf.mspx

http://support.microsoft.com/?kbid=815372

EqualLogic Performance Advantage On ExchangeEqualLogic’s performance advantage has also been specifically demonstrated for Microsoft Exchange through the results of their ESRP report. EqualLogic supported more users with less disks than our competitors, a summary of the results appears below and further information can be obtained on the Microsoft website listed.

Best Practice For Using SQL With EqualLogicTo get the maximum benefits from SQL and a PS Series SAN, you should adhere to the best practices for SQL Server 2000, as outlined by Microsoft and industry experts. In addition, this section describes requirements and recommendations for deploying SQL Server with PS Series storage arrays, including best practices for performance, reliability, scalability, flexibility, and recoverability.

Memory ConfigurationIt is important to properly configure your Windows 2003 server for optimal memory utilization. Memory configuration can affect the database I/O load and performance. An SQL server configured with insufficient memory will generate heavier I/O loads to its databases, while configuring sufficient memory will make your SQL installation more efficient in its use of storage resources. By making your server as tuned and efficient as possible, you can get the maximum benefit from using PS Series storage.

If you run the Microsoft SQL Server Best Practices Analyzer Tool, it will detect if one or more settings need to be corrected. For more information, see the following Microsoft TechNet article: http://www.microsoft.com/downloads/details.aspx?displayla%20ng=en&familyid=B352EB1F-D3CA-44EE-893E-9E07339C1F22&displaylang=en

For SQL Server 2000 memory optimization details, see the Microsoft Knowledge Base article How to determine proper SQL Server configuration settings: http://support.microsoft.com/default.aspx?scid=kb;en-us;319942


http://support.microsoft.com/default.aspx?scid=kb;en-us;319942

http://www.microsoft.com/downloads/details.aspx?displayla%20ng=en&familyid=B352EB1F-D3CA-44EE-893E-9E07339C1F22&displaylang=en

http://www.microsoft.com/downloads/details.aspx?displayla%20ng=en&familyid=B352EB1F-D3CA-44EE-893E-9E07339C1F22&displaylang=en

In addition, you will need to tune the operating system. This procedure is detailed in the Knowledge Base article Large memory support is available in Windows Server 2003 and in Windows 2000: http://search.support.microsoft.com/kb/283037/

Volume ConfigurationSQL Server has a number of different files with different functions that make up the storage installation. A SQL Server instance has multiple databases. For example, each SQL instance includes the following:

System files (master.mdf, master.ldf, model.mdf, model.ldf, msdbdata.mdf, msdblog.ldf, tempdb.mdf, and tempdb.ldf)

Sample database files (pubs.mdf, pubs_log.ldf, northwnd.mdf, and northwnd.ldf) Database files (*.mdf) SQL transaction logs (*.ldf)

The goal when setting up SQL volumes in a PS Series group is to optimize manageability for the size of your environment. You should consider how you will monitor disk usage, in addition to how you will perform backup operations. Some guidelines for creating and setting up SQL volumes are as follows:

Place databases and logs on their own volumes. By default, the SQL installation places the system and user databases and logs on the same volume.

o A small business that needs a simple SQL deployment could put database files (both system and user) on one volume and the logs on another volume.

o A medium-size business that supports multiple databases inside a single SQL instance could create a volume for system databases, a volume for user databases, and a volume for logs.

o A large business running an Enterprise level SQL server instance will need a more complex volume layout. For example, you need a volume for near-static system databases, a volume for the temporary database (TempDB), multiple volumes for user databases, and one or more volumes for logs. It is important to isolate TempDB because of its dynamic nature. This temporary database, which gets recreated every time SQL is started, grows as user database activity increases. Impromptu queries and similar activities will also cause TempDB to grow. With enough activity, TempDB could increase to a size that will consume your entire volume. Isolating this database in its own volume gives you more flexibility and simplifies management.

Create the database and log files as close to their estimated final size. When creating a database, enabling the “Automatically grow file” feature (the default) is recommended to prevent the database or transaction log from becoming full unexpectedly. One of the biggest benefits of PS Series storage is that volumes can be increased dynamically without incurring server downtime, although you must monitor space usage and manually resize the volume.

Defragment SQL file tables. Fragmentation can occur at the file table level. DBCC SHOWCONTIG allows you to determine the amount of index fragmentation. If you have clustered indexes, you can use DBCC DBREINDEX or DBCC INDEXDEFRAG to correct the fragmentation.

Increase the automatic growth percentage. Every time an SQL Server file automatically grows, it must find unallocated space on the volume in the PS Series group. Usually, the space that is allocated will not be contiguous with the current volume space. In fact, the space may come from multiple locations in the PS Series group. The higher the growth percentage, the less often the database will automatically grow, thus limiting the degree of fragmentation.


http://search.support.microsoft.com/kb/283037/

Disable the automatic shrinking of databases. By default, the auto shrink option is disabled. If you allow SQL Server to automatically shrink its size, the space it deallocates will leave fragments of unallocated disk space in the PS Series group. Automatic shrinking of databases should be disabled to reduce fragmentation and overhead. You can use the SQL Server Enterprise Manager to disable the database from shrinking automatically.

Using Backup Exec With EqualLogicBackupExec ConfigurationsVERITAS Backup Exec can be used in a variety of backup and recovery configurations, including the following:

Local backup and recovery. The backup media is directly (locally) attached to the server that is being backed up, and each server runs its own version of the backup software.

LAN backup and recovery. A centralized backup server runs the backup software and backs up other servers (backup clients) by using software agents. The data movement is over a LAN.

SAN backup and recovery. A centralized backup server runs the backup software and backs up other servers (backup clients) by using software agents. The data movement is over a SAN.

Note that backup can be done to either disk or tape, or disk-to-disk-to-tape.

The following diagrams show local, LAN, and SAN backup examples.


Local Backup

LAN Based Backups


SAN Based Backups

Please note that in the above diagram it is not specifically necessary to have an iSCSI tape library, the only requirement is that the server has direct access to a tape drive/library (ie. through a SAN or direct attached).

Using Snapshots To Improve BackupsSnapshots – point-in-time copies of data ⎯ enable you to quickly copy data at the disk (or volume) level. This stable “copy” of data can then be used as the source for your backup operations. Snapshot creation does not disrupt access to the volume. On a PS Series group, the copy is created instantly, usually in a few seconds, and maintained on disk storage in the PS Series group, providing high performance with low disk space utilization and minimal impact on running applications.

Snapshot technology enables you to back up live application data, while ensuring that the data you retrieve from the backup is reliable and useful. Snapshots can be used to stabilize application data in local, LAN, or SAN backup configurations.

Local SnapshotsThe local snapshot operation typically works as follows:

1. Application server prepares for and creates a snapshot, capturing a stable copy of the data. 2. Application server mounts the snapshot and copies data from the snapshot to backup

media. 3. Snapshot is deleted.

The advantage of using snapshots for backup and recovery operations is that snapshots can provide a stable copy of data for copying to backup media. The application is only briefly affected when the snapshot is created, which typically takes a few seconds. Once the snapshot is created, the application server is able to continue application operations, and the snapshot can be backed up. This may safely extend the backup window.

The application server is still involved in moving data from the snapshot to the backup media or backup server. Both full and incremental backups are available with snapshots (including brick level Exchange backups of individual mailboxes).

Restore operations are more reliable, because snapshots ensure the integrity of the backed up data.


SAN SnapshotsThe disadvantage of using local snapshots is that the application server still plays a role in the moving data. While the integrity of the backed up data improves, application server performance may suffer during backup operations.

A serverless backup operation can create a snapshot in the SAN. Then, the backup server can mount the snapshot and copy the data to backup media. This removes the application server from the data copy process, offloading the operation to a backup server on the SAN.

The SAN snapshot (serverless) backup process (diagram below) typically works as follows: 1. Application server prepares for and creates a snapshot, capturing a stable copy of the data. 2. Backup server mounts the snapshot and then copies data from snapshot to backup media. 3. Snapshot is deleted.

Transportable snapshots can improve application performance in your server environment during backup operations. The snapshot provides a stable copy of data for the backup server to copy to backup media. The application is only briefly affected when the snapshot is created, which typically takes a few seconds. Once the snapshot is created, the application server is able to continue application operations, and the snapshot can be mounted and backed up by the backup server. This can dramatically and safely extend the backup window.


VSS (Microsoft Volume Shadow Copy Services) Snapshots And BackupMicrosoft has created a technology in Windows Server 2003 called Volume Shadow Copy Service (VSS). VSS provides a framework for creating snapshots that integrates VSS-aware disk storage (for example, PS Series storage arrays) and applications (for example, Exchange or SQL) with operating system drivers, delivering a turn-key backup solution to IT departments without the need for scripting. There are three required components in the VSS framework:

VSS requestor. Requests the creation of snapshots, typically for backup operations. VERITAS Backup Exec can be used as a VSS requestor.

VSS writer. Business application(such as a database application, e-mail, or file system(that prepares the application for the snapshot creation or data restoration (for example, by flushing buffers, switching logs, etc.). NTFS, Exchange, and SQL are examples of VSS writers.

VSS provider. Mechanism that actually creates and maintains the snapshot in the storage hardware. For example, Auto-Snapshot Manager for Windows is a VSS provider that can create snapshots in a PS Series group.


Thus, you can use EqualLogic Auto-Snapshot Manager (VSS provider) with VERITAS Backup Exec 10 (VSS requester) to backup NFTS, Exchange, and SQL applications (VSS writers), providing an end-to-end backup and restore solution.

A snapshot provides a stable copy of volume data for backups. There are three types of VSS snapshots:

Local software-based VSS snapshots. The backup application is responsible for creating and storing the snapshot of a backup client’s volume. Then, the backup client mounts the snapshot, and the backup server backs up the snapshot.

Local hardware-based VSS snapshots. The backup application requests that the storage hardware create and store the snapshot of a backup client’s volume. Then, the backup client mounts the snapshot, and the backup server backs up the snapshot.

Transportable hardware-based VSS snapshots. The backup application requests that the storage hardware create and store the snapshot of a backup client’s volume. Then, the backup server mounts the snapshot and backs up the snapshot. This moves (offloads) backup processing from the backup client and moves it to the backup server.

Replication Capabilities With EqualLogicBy replicating volumes from one group to another, you can set up a simple, yet robust disaster recovery plan that protects against catastrophic events. Groups can be located in the same building or separated by an unlimited distance. Both on-demand and scheduled replicas are supported.

Similar to a snapshot, a replica represents the contents of the volume at a specific point in time. However, to protect against disaster, a replica must be located in a group (called the secondary group or recovery group) that is not the group where the original volume resides (called the primary group).

If the original volume or the primary group is destroyed, you can recover data by cloning a replica in the recovery group. Cloning a replica creates a volume that contains the volume data that existed at the time the replica was created. Hosts need only be pointed to the new volume location.


You can also promote a replica set. This transforms the replica set into a new volume and snapshots. The new volume will contain the data represented by the most recent complete replica. Each complete replica is transformed into a corresponding snapshot.

Alternatively, you can promote a replica set to a failback volume if the primary group becomes temporarily unavailable, and users can use the promoted failback volume until the primary group becomes available again. At that time you can replicate the failback volume back to the primary group, resume use of the original primary volume, and demote the failback volume on the secondary group to a replica set again. This process is called fast failback.

The default method of transferring data is to use the network connection between the partners. However, if you need to transfer a large amount of volume data for the first replication, and your network link has insufficient speed or bandwidth, you can use the Manual Transfer Wizard to copy the data to external media and then transfer the data to the replica set on the secondary group. After the first data transfer is complete, replication continues, as usual, over the network.

Replication ConfigurationsFor volume replication to occur, two groups must be configured as partners. There arethree options for replication configurations:

One-way replication. One group replicates volumes to another group. Reciprocal replication. Two groups replicate volumes to each other. Centralized replication. Multiple groups replicate volumes to another group.

The diagram below shows one-way replication. AGroup and BGroup are configured as replication partners, with AGroup replicating two volumes to BGroup, which has delegated space to AGroup. From the perspective of AGroup, replication of volumes AVol1 and AVol2 is outbound. From the perspective of BGroup, replication of these volumes is inbound.

The diagram below shows reciprocal replication, in which both groups replicate to each other. In this configuration, AGroup has now delegated space to BGroup for storing its replica sets, and replication of volume BVol1 is outbound from BGroup and inbound to AGroup.


The final diagram below shows a centralized replication configuration, in which two groups are replicating to a third group. In this configuration, CGroup has delegated space to both AGroup and BGroup.

Recovering Volume Data From Replicasto recover volume data from a replica, you can log in to the secondary group and either clone a replica or promote a replica set. These methods of recovering data differ in results and in the amount of space required in the secondary group:

Cloning a replica creates a new volume on the secondary group with the same size and contents as the original volume at the time the replica was created. The replica still exists after the cloning operation, and volume replication from the primary group is not affected. Cloning a replica requires additional space in the secondary group (equal to at least the volume reserve).

Promoting a replica set transforms the replica set into a new volume and a set of snapshots that correspond to each complete replica. The new volume will contain the data represented by the most recent complete replica and can be accessed by initiators as usual. Promoting a replica set does not require additional secondary group space.

When you promote a replica set to a volume, you can choose from these two options:


Permanent promotion. This option discards the replication configuration inherited from the original volume on the primary group. Use this option if the original volume has been destroyed.

Temporary promotion. This option retains the replication configuration inherited from the original volume on the primary group, and keeps track of the changes to the volume once it is promoted and used. Use this option (called failback replication) if you expect to use the new volume only until the original volume is available again (eg. a power outage occurred at the primary site), and plan to replicate the interim changes to the primary group and resume using the original volume.

SummaryBased on a vision of "simplifying networked storage," EqualLogic's peer storage architecture combines advanced software features with fully-redundant, hot-swappable hardware, integrated in a modular chassis design.

EqualLogic's PS Series represents an advancement in storage economics, from purchase and set up to operation and upgrades. Unlike traditional SANs, the EqualLogic PS Series comes complete with all available software features and applications. There is no additional software to install or service costs to incur to initiate any of the data management or protection features you would expect from an enterprise-level SAN. EqualLogic arrays scale on-demand and online allowing you to grow your storage without disrupting your application environment or your budget. This unique packaging model, combined with the ease of use and automated intelligence of the PS Series, enables EqualLogic to provide the greatest return on investment of any storage vendor in the industry.

This architecture and vision delivers an affordable, enterprise-class storage system that is easy to manage and always available, and we therefore believe that an EqualLogic solution is the right choice for CustomerX.


EqualLogic High Level Design Document For CustomerX

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Transcript of EqualLogic High Level Design Document For CustomerX