implementing timefinder vp snap for local replication · this paper describes timefinder® vp snap...

White Paper

Abstract

This paper describes TimeFinder® VP Snap in thin environments on the Symmetrix® VMAX™ Family storage systems for Open Systems platforms. TimeFinder VP Snap is described, as well as associated features for business continuance. Implementation guidelines, including the associated restrictions and/or limitations for this product, are described. Throughout this document, the term EMC® Symmetrix VMAX Family is applicable to all VMAX 10K (VMAXe), VMAX 20K (VMAX) and VMAX 40K Series storage systems. April 2012

Implementing TimeFinder VP Snap for Local Replication Applied technology for thin environments on the Symmetrix VMAX Family

2 Implementing TimeFinder VP Snap for Local Replication

Copyright © 2012 EMC Corporation. All Rights Reserved. EMC believes the information in this publication is accurate as 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. Part Number h10498


Table of Contents

Executive Summary ................................................................................................. 4 Audience ............................................................................................................................ 4 Introduction ....................................................................................................................... 4

TimeFinder VP Snap ................................................................................................. 5 VP Snap operations ............................................................................................................ 6 VP Snap considerations...................................................................................................... 6

Interoperability ............................................................................................................... 7 Environment variables .................................................................................................... 7

Implementing VP Snap ....................................................................................................... 8 Configuring the devices .................................................................................................. 8 Creating a device group .................................................................................................. 9 Using symclone to execute VP Snap sessions ............................................................... 11 Restoring VP Snap sessions ......................................................................................... 19 Cascading with VP Snap ............................................................................................... 22

Conclusion ............................................................................................................ 24

References ............................................................................................................ 24


Executive Summary EMC® Symmetrix® Enginuity™ 5876 is the latest release supporting the Symmetrix VMAX™ Series storage arrays. Enginuity 5876 expands EMC’s leadership in virtual storage by federating and sharing cooperating pools of resources with automation and mobility to enable Infrastructure-as-a-Service (IaaS).

The capabilities of Enginuity 5876 to network, share, and tier storage resources allows data centers to consolidate their applications from dedicated arrays and to deliver new levels of efficiency with increased utilization rates, improved mobility, reduced power and footprint requirements, and simplified storage management.

EMC TimeFinder® technology for local replication is software that provides point-in-time copies of devices that can be used for backups, decision support, data warehouse refreshes, or any other process that requires parallel access to production data. TimeFinder allows users to make copies of data simultaneously on multiple target devices from a single source device.

Enguinity 5876 provides new TimeFinder functionality, called VP Snap that provides space efficient snaps for virtual pool devices. TimeFinder VP Snap provides the efficiency of snap technology with improved cache utilization and simplified pool management.

TimeFinder VP Snap technology, associated features for business continuance, and implementation guidelines, including the associated restrictions and/or limitations for this product, are described herein.

Audience

This white paper is intended for storage administrators, database administrators, and technologists who have an interest in understanding the concepts surrounding TimeFinder VP Snap.

Introduction

EMC introduces the Symmetrix VMAX 40K. The VMAX 40K is a new array that further extends EMC’s lead in high-end storage. Symmetrix VMAX 40K and Enginuity 5876 build on the Symmetrix VMAX foundation of powerful, trusted, smart storage to provide even higher levels of performance, availability, and intelligence in the virtual data center.

The capabilities of Enginuity 5876 to network, share, and tier storage resources allows data centers to consolidate their applications to deliver new levels of efficiency with increased utilization rates, improved mobility, reduced power and footprint requirements, and simplified storage management.

Enginuity 5876 delivers the following new capabilities:

Automation and improved capacity utilization for IBM System z and IBM i environments:

Fully Automated Storage Tiering for Virtual Pools (FAST VP) and Virtual Provisioning™ for IBM System z and IBM i environments

VLUN VP migration support for IBM System z and IBM i environments

Increased efficiency

SRDF® and SRDFe awareness for FAST VP environments


Increased consolidation and reduced TCO

Federated Tiered Storage (FTS) to manage external storage arrays through a VMAX system*

RecoverPoint™ Splitter

TimeFinder® VP Snap

Ease-of-Integration and Management

Unisphere™ for VMAX

Dynamic back end

Federated Live Migration cluster support

* Not available for VMAX 10K (VMAXe).

The features described in this paper apply only to Open Systems environments.

TimeFinder VP Snap TimeFinder VP Snap allows multiple sessions to share capacity allocations within a thin pool, thus reducing the storage required for saved tracks. TimeFinder VP Snap is available with Enginuity 5876 and Solutions Enabler V7.4 and higher. This product is designed to create point-in-time replicas that are conceptually similar to those created by TF/Snap. Both source and target devices must be thin, therefore, the copied data will reside on allocations in a virtual pool. VP Snap sessions are unique because thin pool allocations can be shared among target devices. For example, source updates that are new to multiple point-in-time copies are saved in a single set of allocations that are shared by two or more target devices. When data is copied to more than one target, only a single shared copy resides in the virtual pool, which provides cost-effective space savings.

Figure 1 depicts a source device with three targets that share a single track allocation within the virtual pool.

Figure 1. VP Snap track allocation sharing


VP Snap operations

TimeFinder VP Snap sessions copy data from the source device to the target device only if triggered by a host I/O. Read I/Os to protected tracks on the target device do not result in data being copied.

For a single activated VP Snap session on a source device, the target represents a single point-in-time copy of the source. Copied data resides on allocations in the thin pool. For example, if tracks 100, 200, and 300 are written on the source device, the copied data for each track resides in a unique allocation in the thin pool.

When there is a second VP Snap session from the same source device to a different target, the allocations can be shared. For example, if there is a write to tracks 1,100, 1,200, and 1,300 on the source device, the data is new to both targets' point-in-time, and it can be saved in a single set of allocations that is shared by both target devices.

However, if there is another write to tracks 100, 200, or 300 on the source device, since the data is new for only the second session's point-in-time, when the tracks are copied to the second target device they are put into a set of allocations that are uniquely owned by the second target device. In other words, the allocations for these tracks cannot be shared.

If more VP Snap sessions are added to the same source device, data is copied to the targets based on whether the source data is new with respect to the point-in-time of each copy. When data is copied to more than one target, only a single shared copy resides in the thin pool.

If there is write I/O to one or more of the tracks stored in a shared allocation, the affected allocation for that target will be split off from the shared group because the data is now different than the data for the other targets that are using that allocation. The new data of the written target will be stored in a separate allocation, while the shared allocation will still contain the data of the other targets.

When VP Snap sessions are terminated, the target device is removed from any shared allocations that were part of the session, and any non-shared allocations for that device are de-allocated. When all but one of the VP Snap sessions are terminated, the last remaining session uses the same space in the thin pool, but it is no longer a shared allocation. Upon termination of the last session, the space is de-allocated.

VP Snap considerations

TimeFinder VP Snap has the following characteristics:

• This feature is invoked by using symclone command syntax.

A VP Snap session is created using the –vse attribute, which may only be applied at session creation.

• Support of this feature is limited to Open Systems devices (FBA and AS400 D910 iSeries) and thin-to-thin device clone pairs.

• Cascaded sessions from clone targets will be supported with the following considerations:

Regular TimeFinder/Clone sessions must be in the Copied or Split state for a VP Snap session to be created from its target device.

Incremental restore of VP Snap sessions is not permitted.


The target of a VP Snap session may not be used as a source for any other clone or snap session.

• VP Snap will allow a maximum of 32 sessions on a source device. (This is in addition to the maximum of 16 sessions for traditional TimeFinder/Snap, TimeFinder/Clone, and TimeFinder/Clone Emulation sessions.) Thus a source device may have as many as 48 total sessions.

Differential restores are persistent; this results in increased usage of thin pools.

A differential restore results in an additional session charged to the source device.

• Once created, VP Snap sessions may not be changed to any other mode by using set mode.

• Incremental restores of VP Snap sessions is supported with the following restrictions:

All clone sessions associated with the selected source device must be fully copied or split.

The VP Snap source device may have only one restored session at a time. (This is consistent with all snap and clone behavior.)

Once restored, the only operation allowed is terminate of the restored session.

• Full restore from another session to a VP Snap source device is not supported.

• The Clone Larger Target feature is not supported.

Interoperability

Interoperability with other EMC Symmetrix software products is as follows:

SRDF

• The use of R2 devices as VP Snap sources require that SRDF/A device-level Write Pacing is configured with autostart on the R1 side, or that the device-level Write Pacing is activated and supported on the SRDF/A session.

• A TimeFinder VP Snap target cannot be an RDF device.

ORS

• TimeFinder VP Snap source devices may be used as the control device of ORS push operations, but not pull operations. A VP Snap target device is not permitted to be used with ORS.

FAST VP • VP Snap source and target devices are optimized by FAST VP, however, the shared target

allocations will not be moved.

Environment variables

Users can specify an environment variable to change the default TimeFinder/Clone copy mode. Set SYMCLI_CLONE_COPY_MODE to determine the type of clone session that will be created by default. A new copy mode VSE_NODIFF is available for VP Snap sessions,


however, if the user specifies -precopy, -copy, or -nocopy during the create, the default is overridden. The following example displays the available clone copy modes.

SYMCLI_CLONE_COPY_MODE specifies the mode in which clone sessions are created. This variable can be set to NOCOPY_NODIFF, COPY_NODIFF, PRECOPY_NODIFF, COPY_DIFF, PRECOPY_DIFF, or VSE_NODIFF.

Implementing VP Snap

Implementing VP Snap requires a series of steps to ensure that the proper devices are available, to verify the existence of a virtual pool where target devices will reside, and to create VP Snap sessions.

Note that the following tests can be run on all Symmetrix VMAX Family storage systems.

1. Ensure that the systems are running Enginuity 5876 and SE 7.4.

2. Execute the following commands to display the Enginuity level and Solutions Enabler (SE) code release:

symcfg list

symcli

Configuring the devices Configuring devices and creating a thin pool is optional. Users may choose to use devices and a thin pool that already exists. The instructions that follow are mainly a guide in the event that configuring a new environment is required.

1. Create TDEV devices for tests.

symconfigure -sid 455 commit -nop -cmd "create dev count=64, size=4GB, emulation=fba, config=TDEV;"

2. Show current thin pools on the storage array

symcfg -sid 455 list -pool

3. Create a thin pool named VSE.

symconfigure -sid 455 -cmd "create pool VSE type=thin;" commit -nop

4. Create DATA devices.


symconfigure -sid 455 -cmd "create dev count=8, config=RAID-5, data_member_count=7, disk_group=5, attribute=datadev, emulation=fba, size=16344;" commit -nop

5. Add data devices to thin pool.

symconfigure -sid 455 -cmd "add dev 527:52e to pool VSE type=thin, member_state=enable;" commit -nop

6. Bind TDEV devices to the pool.

symconfigure -sid 455 -cmd "bind tdev 4df:4ed to pool VSE;" commit –nop

7. Display the pool devices.

symcfg show -sid 455 -pool VSE -detail –thin

Creating a device group

1. Create a device group to simplify the manipulation of devices during testing. Add the source and target devices that will be used for the TimeFinder VP Snap sessions.

symdg create testdg

symld –sid 455 –g testdg add dev 4df

symld –sid 455 –g testdg addall –RANGE 4df:4ed -tgt

2. Using SYMCLI output, determine the Symmetrix logical device names and the Symmetrix device ID’s.

symdg show testdg


Using symclone to execute VP Snap sessions

1. Display the status of the thin pool to determine space and track allocations.

a. Review the number of allocated and shared tracks in the pool.

Note the source device’s allocated and shared track percentages. As in most customer environments, the source device contained data before the start of the test, therefore, Total Written Tracks is already at 25 percent.


2. Using the device group, created earlier, execute the SYMCLI symclone command to create and

activate four VP Snap sessions..

symclone –sid 455 –g testdg create –vse DEV001 sym ld TGT001 –nop

symclone –sid 455 –g testdg activate DEV001 sym ld TGT001 –nop

symclone –sid 455 –g testdg create –vse DEV001 sym ld TGT002 -nop

symclone –sid 455 –g testdg activate DEV001 sym ld TGT002 -nop





a. Query the result.

symclone list –vse


Note the V and X target device flags and the definitions provided in the legend below.

3. After the initial activation, all written tracks on the source device are protected (shown in the previous legend). Allocations can only be shared when a second VP Snap session (from the same source device) is created using a different target.

a. Review the thin pool details to see that the allocated and shared tracks have not changed.


Note that 04DF is the source device, and that 04EA, 04ED are the target devices.

4. Create and activate four additional VP Snap sessions.

symclone –sid 455 –g testdg create –vse DEV001 sym ld TGT001 –nop








5. Query the VP Snap sessions. Each session contains the same number of protected tracks.

symclone list –vse


6. Display the results of the IOmeter utility, which was used to generate I/O to the source device.

7. After the second set of write I/Os is replicated to the eight target devices, the number of allocated tracks and the number of shared tracks in the pool has increased.


8. To determine the amount of space savings, compare the allocated tracks between VP Snap sessions and clone copy sessions.

a. By terminating the VP Snap sessions and using the same devices to create regular –copy

clones, the full benefit and space efficiency of VP Snap can be seen.


In concluding this test, note that the allocated tracks after activating the regular –copy clones (with 414528) consume almost four times the allocated tracks with the VP Snap –vse clones (with 127392).


Restoring VP Snap sessions

Additionally, VP Snap provides the ability to perform Incremental Restores. Target data is not de-allocated since the restored session are persistent until all sessions have been terminated.

1. Execute a restore for each target device. Each session must be restored and then terminated before moving onto the next session.

symclone –sid 455 –g testdg restore DEV001 sym ld TGT001 –nop

2. Review the status of the restore.

symclone –sid 455 –vse list

3. Review the thin pool details for each restored session. Notice that the target tracks are not de-allocated.

symcfg show -sid 455 -pool VSE -detail –thin


4. Terminate the restored target session and then display the results. VP Snap restore operations maintain the original session, so that when a VP Snap session is restored, both the original CopyOnWrite session and the restore session exist. In this case, the restored session must be terminated before the original session.

symclone -sid 455 -g testdg terminate -restored DEV001 sym ld TGT004

5. Terminate the original copy session in order to eliminate and de-allocate tracks from the thin pool.

symclone -sid 455 -g testdg terminate DEV001 sym ld TGT001 –nop

6. Examine the device group and the thin pool VSE.

symclone –sid 455 –vse list


Note that when the target number (TGT#) is not specified, the VP Snap sessions are terminated in order, from oldest session to newest session.

7. The tracks are de-allocated from the thin pool only after the original VP Snap session has been

terminated..

symcfg show -sid xxx -pool VSE -detail –thin

Many users prefer using device files, as opposed to using device groups. The following commands highlight the appropriate syntax when using a device file.

symclone –sid 455 –f test.txt create –vse

symclone -sid 455 -f test.txt activate

symclone -sid 455 -f test.txt restore

symclone -sid 455 -f test.txt terminate –restored

symclone -sid 455 -f test.txt terminate


Cascading with VP Snap

Basic cascading with TimeFinder VP Snap is supported with Enginuity 5876 and TimeFinder/Clone. Cascading operations are supported when a user creates a full-device TimeFinder/Clone session, and then creates a VP Snap session.

Running the VP Snap session off the full-device clone concurrently is allowed, as long as the copies are activated sequentially, preserving the copy direction. Figure 2 describes the co-existence of a cascading clone and a VP Snap target where the AB session is a full–device TimeFinder/Clone, and the BC leg is a clone to VP Snap target.

Figure 2. Cascading Clone and VP Snap

Cascading features are restricted in the initial release of 5876 as follows:

• Clone sessions must be in the Copied or Split state before creating a VP Snap session from the target device.

• Incremental restore of VP Snap sessions is not permitted. • The clone session must exist before the target device is used as a VP Snap source. Creating a

clone session using a VP Snap source as the target device is not permitted. • The target of a VP Snap session cannot be used as the source for any other clone or snap

session.

• VP Snap is not supported with Clone Emulation mode.

Implementing Cascading Clone and VP Snap

To implement cascading clone and VP Snap, two device files are created. Leg1.txt for the AB full device clone, and leg2.txt for the BC VP Snap session devices. The contents of these files are displayed below.


1. Create and activate the full device clone session.

symclone -sid 455 –f leg1.txt create –precopy -nop

symclone –sid 455 –f leg1.txt activate -nop

2. Query the results.

symclone –sid 455 –f leg1.txt query

Note the target device settings.

3. Once the target device is in a Copied state, create the VP Snap session.

symclone -sid 455 –f leg2.txt create –vse -nop

symclone –sid 455 –f leg2.txt activate –nop

symclone –sid 455 list


Conclusion TimeFinder VP Snap allows multiple target sessions to share capacity allocations within a thin pool, thus reducing the storage required for saved tracks. VP Snap is conceptually similar to the use of TimeFinder/Snap, however, it works only with thin devices and is invoked by the SYMCLI symclone command syntax. Multiple VP Snap sessions can share up to 32 thin pool allocations (or 16 differential sessions), which allows users to maximize their thin pool resources. VP Snap is easy to manage and combines the benefits of both full clone and space-saving snap technologies.

References Reference information and product documentation can be found at www.powerlink.emc.com including:

• EMC Symmetrix TimeFinder Product Guide

• EMC Solutions Enabler Symmetrix TimeFinder Family CLI Product Guide

• EMC Symmetrix TimeFinder for VMAXe Product Guide

http://www.powerlink.emc.com/

implementing timefinder vp snap for local replication · this paper describes timefinder® vp snap...

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