migrating data from an emc clariion array to a vnx platform

White Paper

Abstract

This white paper provides best practices for migrating data from an EMC block-storage array (such as a CLARiiON® AX or CX™ array) to one of EMC’s new VNX™ arrays. It includes simple step-by-step instructions on how to use EMC® SAN Copy™ to perform the migration. If you wish to migrate data from an EMC file-storage array (such as a Celerra® NS array), please refer to the white paper Migrating Data from an EMC Celerra Array to a VNX Platform Using Celerra Replicator. February 2011

MIGRATING DATA FROM AN EMC CLARiiON ARRAY TO A VNX PLATFORM USING SAN COPY A “how-to” guide featuring best practices

2 Migrating Data from an EMC CLARiiON Array to a VNX Array Using SAN Copy

Copyright © 2011 EMC Corporation. All Rights Reserved. EMC believes the information in this publication is accurate of its publication date. The information is subject to change without notice. The information in this publication is provided “as is”. EMC Corporation makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com. All other trademarks used herein are the property of their respective owners. Part Number h8173


Table of Contents

Executive summary.................................................................................................. 4

Audience ............................................................................................................................ 4

Overview ................................................................................................................. 4

The difference between a push and pull migration ......................................................... 4

How to use SAN Copy to perform a push migration from a CLARiiON to a VNX ............ 5

What you need to know before using this procedure .......................................................... 5

The step-by-step procedure ................................................................................................ 6

Other SAN Copy best practices and considerations ................................................. 20

Speeds ......................................................................................................................... 20

LUN technologies and mobility considerations ............................................................. 21

Conclusion ............................................................................................................ 25

References ............................................................................................................ 25


Executive summary EMC’s new VNX™ series of midrange storage arrays features major architectural innovations such as the new SAS back end. The point-to-point architecture of the SAS back end offers higher availability and better performance than older architectures such as Fibre Channel.

This white paper serves as a migration guide to help you move data from an EMC midrange block-storage array (such as a CLARiiON® CX™ or AX model) to a VNX storage array. It provides simple step-by-step best practices that show you how to use EMC’s SAN Copy™ software to perform a low/no-cost migration of data to your VNX, so that you can start taking advantage of the VNX technology as quickly as possible. If you wish to change existing traditional LUNs to thin pool LUNs, you may use data migration as an opportunity to do so. Table 5, Table 6, and Table 7 starting on page 23 provide rules on allowable destination LUN types.

If you need to migrate data from one of EMC’s file-storage arrays (such as a Celerra® NS model), please refer to Migrating Data from an EMC Celerra Array to a VNX Platform Using Celerra Replicator.

Audience

This white paper is for customers who have purchased an EMC VNX series array and wish to migrate their data from a previous-generation EMC block-storage array to the VNX series hardware. It also serves as a guide for EMC field services and customer service employees. While familiarity with SAN Copy is a plus, it is not required.

Overview To help ensure a smooth transition for customers who wish to migrate their data from older EMC midrange arrays to the powerful new VNX platforms, EMC supports a wide range of data migration tools and techniques. EMC recently performed numerous tests to pinpoint the most efficient way to use these tools to migrate data to a VNX platform. After careful testing, EMC concluded that the most effective way to migrate data from a file-based array (such as a Celerra NX model) is to utilize Celerra Replicator™, which is described in Migrating Data from an EMC Celerra Array to a VNX Platform Using Celerra Replicator.

On the other hand, our tests showed that when migrating from a block-based array (such as a CLARiiON AX or CX model), the most effective tool is EMC’s SAN Copy. The rest of this white paper provides a step-by-step procedure, including best practices, to help you make a smooth transition to your new VNX platform.

The difference between a push and pull migration

SAN Copy is a software tool that is pre-loaded on EMC midrange storage arrays. You must install SAN Copy Enabler before using SAN Copy. While this is usually a


chargeable product, the enabler is free for VNX customers who wish to perform a data migration from an older-generation array (such as a CLARiiON) to a VNX storage array. Before installing the enabler, you should decide whether you are going to use SAN Copy to push or pull the data. The advantages of each method are explained next and summarized in Table 1.

In the pull method, the SAN Copy Enabler is installed on the VNX platform, and the SAN Copy software on the VNX performs the migration by “pulling” the data from the older CLARiiON array and storing it on the VNX. This method allows SAN Copy to run on VNX’s more powerful processor. Another advantage of the pull method is that the VNX is likely to have less data and host I/O traffic, which the SAN Copy operation could impact.

In the push method, the SAN Copy Enabler is installed on the CLARiiON array, and the CLARiiON SAN Copy software “pushes” the data onto the VNX platform. The push method is usually faster than the pull method. Also, unlike a pull, the push supports “incremental” copies. This allows the LUN(s) to remain online during most of the migration; the migrating LUN only needs to be brought offline for the final synchronization and cutover from the source LUN to the new destination LUN on the VNX platform. Because of these advantages, EMC recommends that you use the push method to perform a migration to your new VNX platform.

Table 1. SAN Copy push migration versus SAN Copy pull migration

A step-by-step procedure for using SAN Copy for a push migration is provided next.

How to use SAN Copy to perform a push migration from a CLARiiON to a VNX

What you need to know before using this procedure

NOTE: The volume of data and the number of attached hosts can dramatically impact the complexity of a data migration. The following SAN Copy data migration procedure is intended for CLARiiON arrays that have less than 10 TB of data, and fewer than 20 attached hosts. If your CLARiiON array has more than 10 TB of data, and/or more than 20 attached hosts, EMC strongly recommend you engage Professional Services from EMC, or an EMC partner, to execute your data migration to VNX.

SAN Copy push SAN Copy pull Migration speed Faster Slower Greater CPU burden Higher CPU burden on

source array Higher CPU burden on destination array

Supports incremental Yes No Can LUNs be online during initial sync/migration?

Yes No


Most steps in this procedure use the Unisphere™ GUI or the SAN Copy Wizard. However, in a few cases, where this is either not possible or advantageous, the steps are performed using a naviseccli command.

This procedure starts by installing the SAN Copy Enabler on your CLARiiON array. It then uses SAN Copy to perform incremental push operations to migrate existing (source) LUNs on your CLARiiON to destination LUNs on your new VNX series array.

The step-by-step procedure

Back up your data

Before you perform any operation that involves manipulating your data, including this migration procedure, EMC highly recommends that you perform a full backup of your data.

Step 1

Using the new Unisphere Service Manager (USM) or the older Navisphere® Service Taskbar (NST), install the appropriate SAN Copy Enabler on your CLARiiON array. The SAN Copy Enabler is going to be included for free on VNX platforms. There will be a zero-cost SAN Copy Enabler available for older-generation arrays (CLARiiON CX4 series, for example) for customers who wish to perform data migrations to the VNX platform.

Step 2

Configure at least one path between a CLARiiON SP port and VNX SP port. You can do this using the native switch-management tools to zone CLARiiON SP port(s) to VNX SP port(s), or by installing direct connections between the CLARiiON SP port(s) and VNX SP port(s). One advantage to configuring multiple paths is that SAN Copy will spread out concurrent SAN Copy operations among available paths, making the migration faster. For more recommendations on SAN Copy zoning best practices, see the Chapter 2 section “SAN Copy zoning requirements and recommendations” in the EMC SAN Copy for Navisphere Administrator’s Guide. Powerlink® access is required to access this guide.

Step 3

On the CLARiiON array, click the Replicas tab, and then click Update SAN Copy Connections. You should get successful update messages for both SP-A and SP-B, as shown in Figure 1 and Figure 2.

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/Technical_Documentation/069001188.pdf

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/Technical_Documentation/069001188.pdf


Figure 1. SAN Copy LUNs: Source and destination


Figure 2. SAN Copy LUNs: Source and destination update message

Step 4

On the VNX platform, create destination LUN(s) for the source LUNs that you wish to migrate from the CLARiiON. The destination LUNs must be at least the same size as their source LUNs, but the RAID types do not have to match the RAID types of the source LUNs. It is often useful to use the same LUN numbering on the source and destination LUNs to reduce confusion.

Step 5

On the VNX platform, you will need to have a storage group that will be used to present the destination LUNs to the older array for the purposes of the data migration. Create or identify a storage group for this purpose. Put the destination LUNs into the storage group by clicking yes when Unisphere asks if you wish to connect LUNs to the storage group immediately after storage group creation, or by selecting Connect LUNs on an existing storage group.


Step 6

Connect the CLARiiON system ports to the storage group in the VNX in which the destination LUNs reside; this makes the destination LUNs available to the CLARiiON array. To do this:

Right-click the SAN Copy storage group on the VNX platform.

Click the SAN Copy Connections tab.

In the pull-down menu, select the appropriate CLARiiON. At least one port should appear under Ports to connect.

Highlight the desired port.

Click the Advanced button to display all available potential connection paths that are present/zoned.

Select the desired paths as shown in Figure 3.

Figure 3. Selecting SAN Copy connections


Step 7

Determine the WWN of your destination LUN by clicking LUNs from the Storage tab on the VNX platform; highlighting the destination LUN; and clicking Properties. In the LUN Properties window, the WWN of the LUN will be its Unique ID. Write this Unique ID down. This is shown in Figure 4.

Figure 4. Determining the WWN of the destination LUN

Step 8

Since we will be doing an incremental copy migration, you need to create and add LUNs to a reserved LUN pool on the source CLARiiON array. You need at least one reserved LUN for each incremental SAN Copy source LUN. The LUNs can be smaller than the LUN(s) to be migrated, as they are used for tracking changes to the source LUN during the incremental copy. Best practice is to create two LUNs for each LUN to be migrated, each 10 percent of the size of the LUN to be migrated. Create the required number of LUNs and then add them to the reserved LUN pool.

To add LUNs to the reserved LUN pool, click the Replicas tab on the VNX platform, and click Configure Reserved LUN Pool. Add LUN(s) to the reserved LUN pool, as shown in Figure 5.


Figure 5. Adding LUNs to the reserved LUN pool

Step 9

Click the Replicas tab on the VNX platform, and click SAN Copy Wizard to open the SAN Copy Wizard, as shown in Figure 6.


Figure 6. Opening the SAN Copy Wizard

Step 10

Click Next In the Welcome screen to open a list of arrays in the domain that have SAN Copy installed, and select the desired VNX platform. In our case, this is the VNX platform that has the destination LUN(s).

Step 11

The wizard’s next screen asks if you desire a full or incremental session. Select Incremental to minimize the amount the downtime during the migration. Click Next.

Step 12

Select the source LUN(s) from the list of available LUNs. You can select multiple LUNs by holding down the Control key while you select LUNs. You can sort this list on any of the column headers. Once the LUN(s) have been selected, click Next.


Step 13

The next screen displays the LUN(s) you selected for the migration, and asks you to right-click each source LUN to choose its destination LUN. Select the destination LUNs for the source LUNs as shown in Figure 7.

Figure 7. Selecting storage destinations

Step 14

In the SAN Copy Select Destination Storage window, your VNX platform will probably not appear in the pull-down list of available systems. This is because the array needs to be in the same domain, and in the initial release of VNX we are not supporting multiple arrays in the same domain. To select the correct destination LUN, you must click the Enter WWN button on the bottom left of the window, and enter the destination LUN’s WWN that you noted in step 7. This is shown in Figure 8.


Figure 8. Selecting the destination LUN

Step 15

After you enter the WWN of the destination LUN and click OK, select the Verify Connections checkbox and click Next, as shown in Figure 9.


Figure 9. Verifying connections

Step 16

Select a Link Bandwidth value and click Next. Some older arrays may only support a maximum bandwidth of 2048. Here is a best practices excerpt from the SAN Copy release notes:

Performance notes For best performance of incremental copies on a Fibre Channel connection, enter a

bandwidth of 4096 on CX4 storage systems and modify the latency to 0.5 ms in the session properties.

For sessions on a 10 Gb iSCSI connection, data digest and header digest should be disabled in the iSCSI connection set options.

Step 17

Select a throttle value. This value ranges from 1 to 10, with 10 being the fastest. It defaults to 6. If you experience poor host I/O performance on the source array during


SAN Copy migration sessions, then you may select a lower throttle value, but this will result in much longer SAN Copy migration durations.

Step 18

Review your choices and click Finish to create your SAN Copy session.

Step 19

By default, the number of concurrent SAN Copy sessions per SP is limited to 4. This value can be changed for each storage processor under the Replicas tab by clicking Configure SAN Copy Settings as shown in Figure 10. Increasing the number of concurrent SAN Copy sessions per SP will allow more SAN Copy sessions to run at the same time, which may make the migration process faster if you plan to migrate multiple LUNs. But increasing the number of concurrent SAN Copy sessions per SP will also increase the utilization on each SP, and that can potentially negatively impact your I/O response time during the data migration. Keep this trade-off in mind when considering how many concurrent SAN Copy sessions to allow.

Figure 10. Selecting the number of concurrent SAN Copy sessions per SP


Step 20

Although a SAN Copy session can be started from the GUI, you can make an incremental SAN Copy session run faster if you start it using the Naviseccli CLI. This also reduces performance impact to production data during the bulk copy, because it does not execute any copy-on-first-writes, which can be costly in terms of performance.

When you use this method, you need to be aware that the session will not be fully “in sync” at the end of the copy. As a result, more areas of data will need to be synced during the follow-up sync operation that occurs during an offline cutover window. However, this is generally not a problem, and this command line option for starting a session is the most commonly used method in the field because of its performance benefits. The Naviseccli command line alternative to using the GUI to start the incremental session is as follows:

Naviseccli –h <sp_ip_address_of_sancopy_source_array> -user <user> -password

<password> -scope 0 sancopy –start –name sessionName –copywholelun –nomark

all

Step 21

After successfully starting the incremental SAN Copy session, go to SAN Copy Sessions under the Replicas tab; click the Sessions sub-tab and highlight the started session, then click Status to monitor the status of the copy, as shown in Figure 11.


Figure 11. Monitoring the status of the SAN Copy session

Step 22

When the status changes to Completed, as shown in Figure 12, the incremental SAN Copy migration is done. However, the destination may not be fully in sync with the source LUN, because after an incremental copy all changes to the source LUN are tracked but not automatically updated to the destination.


Figure 12. Completed status

Step 23

Schedule a brief offline window to cut over production from the source LUN on the CLARiiON array to the destination LUN on the VNX platform. Before switching over, you must prepare the source LUN by quiescing I/O and flushing buffers as required by your host’s operating system

Step 24

During the offline window, remove the source LUN from the storage group on the source CLARiiON array. This causes temporary data unavailability to the host(s) but is a necessary action when preparing to cut over to the newly copied LUN on the VNX.

Step 25

On the VNX platform, synchronize the SAN Copy incremental copy session by clicking SAN Copy Sessions under the Replicas tab, selecting the appropriate SAN Copy session, and clicking the Start button.


You may monitor the status of this incremental sync through the Status button. This is similar to steps 21 and 22, except that since this operation only needs to synchronize the data that has changed since the first incremental copy operation, this should complete much faster than the original sync.

Step 26

When this is completed, delete the SAN Copy session.

Step 27

The SAN Copy destination LUNs on the VNX need to be accessible to your host(s). Ensure that your hosts are properly cabled/zoned to the VNX platform. On the VNX platform, remove the SAN Copy destination LUNs from the storage group that they were in during the SAN Copy migration operation, and put these LUNs as well as the desired hosts into a new storage group.

Step 28

Ensure that the production host can see the new LUN, and that it is mounted/mapped as desired.

Step 29

The data migration to the new VNX platform is completed. You may bring the production host back online and resume normal operations with your LUN(s) now residing on the new VNX platform.

Other SAN Copy best practices and considerations

Speeds

There are many factors and caveats that come into play when stating maximum achievable SAN Copy bandwidth numbers, such as hardware model; FLARE® revision; disk type and speed; throttle settings; write aside value; caching; number of concurrent sessions; workload; and so forth. Table 2 lists the maximum-achievable SAN Copy bandwidth numbers as measured in FLARE release 29 (not expected to have changed much for release 30) on the various CX4 models. These numbers are for a single 8 Gb Fibre Channel connection to a destination array using incremental SAN Copy, initial sync, bulk copy, local connection, max concurrent sessions, and a throttle setting of 10.


Table 2. Achievable capacity

*WA = your “write aside” setting (that is, the largest size data that will get mirrored across SP cache)

Your two-SP bandwidth is approximately 2x the single-SP bandwidth when bypassing cache, and about 1.8x the single SP bandwidth when using cache. The local connection bandwidth measured over 10 Gb iSCSI maxed out at 300-350 MB/s using a CX4-960 array. In general, the initialization bandwidth for iSCSI was about .6 to .8 that of 8 Gigabit Ethernet Fibre Channel.

These numbers are provided only for general guidance, and are examples of maximums using arrays that were dedicated to nothing other than SAN Copy migrations using maximum available CPU utilization. Many factors, including customer workload, may result in significantly slower rates when used on production arrays. Please consult an EMC CSPEED guru for more details.

LUN technologies and mobility considerations

The EMC white paper EMC SAN Copy - A Detailed Review provides a detailed discussion on LUN technologies and mobility considerations and a review of SAN Copy in general. The following tables are excerpts from this white paper and are provided for your quick reference with regard to SAN Copy limits, as well as LUN mobility rules and considerations.

http://www.emc.com/collateral/software/white-papers/h2099-emc-clariion-san-copy-wp.pdf


Table 3. CX4 series SAN Copy limits

Storage system CX4-960, CX4-480 CX4-240, CX4-120

Maximum concurrent sessions

16 8

Maximum destinations per session 100 50

Maximum incremental source LUNs

512 (Release 29)

100 (Release 28)

256 (Release 29)

50 (Release 28)

Maximum defined incremental sessions1

912 (Release 30)

300 (Releases 28-29)

512 (Release 30)

150 (Releases 28-29)

Maximum incremental sessions per source LUN2

8 8

Table 4. CX3, CX, and AX series SAN Copy limits

Storage system CX3-80, CX3-40, CX3-40c, CX700, CX600

CX3-20, CX3-20c, CX3-10, CX500, CX400

AX4-5, AX4-5F8

Maximum concurrent sessions3 16 8 4

Maximum destinations per session 100 50 50

Maximum incremental source LUNs4 100 50 64

Maximum defined incremental sessions 300 150 25

1 These limits include MirrorView™/A images and SnapView snapshot source LUNs in addition to the incremental SAN Copy logical units. The maximum number of source LUNs assumes one reserved LUN assigned to each source LUN. 2 These limits include MirrorView/A images and SnapView sessions in addition to the incremental SAN Copy sessions. 3 Running multiple SAN Copy sessions can improve the overall transfer rate; however, it can also slow down other active host I/O during the copy session. 4 This total is shared with MirrorView/Asynchronous and SnapView. Each source LUN for these applications requires at least one LUN from the reserved LUN pool. This number is actually the total number of LUNs that can be allocated to the reserved LUN pool.


Table 5. Remote SAN Copy session summary to a thin LUN destination

Copy Direction Source Destination Result

Push

Thick or RAID group LUN R29, R30 thin Full

R29, R30 thin LUN R29, R30 thin Thin

Thin, thick, RAID group LUN Third-party thin Full

Thin, thick, or RAID group R28.5 thin LUN Full

Pull Thick, RAID group, third-party LUN R30 thin LUN Thin

Thick, RAID group, third-party LUN R29 thin LUN Full

Table 6. Local SAN Copy session summary to a thin LUN destination

Release Source Destination Result

R30 Thick or RAID group LUN Thin LUN Thin

R29 RAID group LUN Thin LUN Full

R29 or later Thin LUN Thin LUN Thin

Table 7. LUN Migration rules for SAN Copy

LUN type Migrate to same size LUN Migrate to larger LUN

Source LUN on SAN Copy CLARiiON (push) Can be migrated* Destroy session before migration

Destination LUN on remote CLARiiON (push) Can be migrated* No restriction

Destination LUN on SAN Copy CLARiiON (pull) Can be migrated* Destroy session before migration

Source LUN on remote CLARiiON (pull) Can be migrated* No restriction

Reserved LUN (incremental SAN Copy) Cannot be migrated

*A session cannot be created on a LUN that is migrating.


Table 8. Valid VNX LUNs

LUN type Valid source for a full SAN Copy session?

Valid source for an incremental SAN Copy session?

LUN, metaLUN, thick, or thin LUN is not in use with any replication software. (Release 29 required for thin LUNs. Release 30 required for thick LUNs.)

Yes (Caution – source LUN should not change during the copy)

Yes

SnapView snapshot Yes No (Incremental sessions use snapshots internally)

SnapView clone Yes (Caution – source clone should not change during the copy)

Yes

MirrorView source LUN Yes (Caution – source LUN should not change during the copy)

Yes

MirrorView destination LUN No (A snapshot of the LUN may be used as a SAN Copy source)

Yes

Symmetrix TimeFinder® BCV Yes (Caution – source should not change during the copy)

No

Symmetrix TimeFinder snap Yes (Caution – source should not change during the copy)

No

If MirrorView (meaning MirrorView/Synchronous and/or MirrorView/Asynchronous) is installed on the storage system, then SAN Copy cannot use the MirrorView port. However, if MirrorView is not installed on the storage system, then SAN Copy can use all of the ports.


Conclusion EMC recommends using EMC SAN Copy as the preferred tool for migrating block data from AX and CX series CLARiiON arrays to the new VNX series platform. This white paper provides a no-cost, step-by-step procedure for customers to migrate existing block data using an incremental push operation with SAN Copy. Documenting the SAN Copy operation as an incremental push was done to both optimize performance and minimize downtime. Users wishing to migrate file data from a Celerra to a VNX series platform should consult the peer white paper Migrating Data from an EMC Celerra Array to a VNX Platform Using Celerra Replicator available on Powerlink.

References The following documents are available on EMC.com and Powerlink except where noted:

EMC SAN Copy - A Detailed Review white paper EMC SAN Copy for Navisphere Administrator’s Guide (Powerlink only) Migrating Data from an EMC Celerra Array to a VNX Platform Using Celerra

Replicator white paper

http://www.emc.com/collateral/software/white-papers/h2099-emc-clariion-san-copy-wp.pdf

migrating data from an emc clariion array to a vnx platform

Documents