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Hitachi Virtual Storage PlatformHitachi Copy-on-Write Snapshot User Guide

MK-90RD7013-11


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Hitachi Virtual Storage Platform Hitachi Copy-on-Write Snapshot User Guide

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© 2010 - 2014 Hitachi, Ltd. All rights reserved.

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purpose without the express written permission of Hitachi, Ltd.

Hitachi, Ltd., reserves the right to make changes to this document at any time without notice and assumesno responsibility for its use. This document contains the most current information available at the time ofpublication. When new or revised information becomes available, this entire document will be updated and

distributed to all registered users.

Some of the features described in this document might not be currently available. Refer to the most recentproduct announcement for information about feature and product availability, or contact Hitachi DataSystems Corporation at https://portal.hds.com.

Notice: Hitachi, Ltd., products and services can be ordered only under the terms and conditions of theapplicable Hitachi Data Systems Corporation agreements. The use of Hitachi, Ltd., products is governed bythe terms of your agreements with Hitachi Data Systems Corporation.

Notice on Export Controls. The technical data and technology inherent in this Document may be subjectto U.S. export control laws, including the U.S. Export Administration Act and its associated regulations, andmay be subject to export or import regulations in other countries. Reader agrees to comply strictly with allsuch regulations and acknowledges that Reader has the responsibility to obtain licenses to export, re-export,or import the Document and any Compliant Products.

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Sizing the data pool workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6Calculating the number of Copy-on-Write Snapshot pairs . . . . . . . . . . . . . . . . 2-7

Calculating SS pairs when creating external volumes or V-VOLs . . . . . . . . . 2-7Calculating maximum SS pairs based on differential tables workflow . . . . . 2-7Calculating maximum SS pairs based on shared memory workflow. . . . . . . 2-9

Calculate the capacity of the pool management block . . . . . . . . . . . . . 2-11Capacity of pool association information . . . . . . . . . . . . . . . . . . . . . . 2-12

Calculating maximum pairs based on pair tables. . . . . . . . . . . . . . . . . . . 2-12Determining maximum pairs allowed on your system . . . . . . . . . . . . . . . 2-12Planning for splitting pairs in consistency groups . . . . . . . . . . . . . . . . . . . . . 2-12

Requirements and restrictions for the At-Time Split operation . . . . . . . . . 2-13Pair inclusion in At-Time Split operations workflow . . . . . . . . . . . . . . . . . 2-13Consistency maintenance workflow when sharing SS P-VOLs with UR or TCvolumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14Snapshot secondary volume consistency maintenance . . . . . . . . . . . . 2-16

External volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16External-volume failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

3 Copy-on-Write Snapshot installation and configuration. . . . . . . . . . 3-1Installing and removing Copy-on-Write Snapshot . . . . . . . . . . . . . . . . . . . . . . 3-2Configuration workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2Creating data pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2Creating V-VOLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4Setting up the Command Control Interface command device . . . . . . . . . . . . . . 3-5

4 Sharing Copy-on-Write Snapshot volumes. . . . . . . . . . . . . . . . . . . 4-1

Interoperability with other software applications and functions . . . . . . . . . . . . 4-2The Data Retention Utility and access attributes. . . . . . . . . . . . . . . . . . . . . . . 4-3

Dynamic Provisioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4Resource Partition Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5ShadowImage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Restrictions when sharing P-VOLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7TrueCopy and Universal Replicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

TC and UR volume backup in 3DC multi-target configuration . . . . . . . . . . . 4-8 Volume Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9Thin Image. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

5 Pair operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Pair operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2Checking the pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2Pair creation workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Pair creation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3Configuring pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Removing and moving volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4


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Creating pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5Pair split . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Splitting pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10Splitting pairs in consistency groups at a pre-determined time . . . . . . . . . 5-10

Pair resynchronization and restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11Resynchronizing and restoring pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Pair deletion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Deleting pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

6 Copy-on-Write Snapshot monitoring and maintenance. . . . . . . . . . 6-1

Monitoring the storage system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2Monitoring pair information, license capacity, status . . . . . . . . . . . . . . . . . 6-2

Pair status definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2Monitoring pair properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3Monitoring synchronous rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Monitoring consistency groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Monitoring pair operations history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Monitoring pool information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Maintaining the storage system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6Managing data pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Increasing data pool volume capacity . . . . . . . . . . . . . . . . . . . . . . . . . 6-6Changing pool volume threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7Changing pool volume names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7Recovering pool volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8Deleting pool volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

Managing virtual volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8Changing virtual volume names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9Deleting virtual volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

Switching off the storage system power and replacing the microcode . . . 6-10Switching off the power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10Replacing the microcode offline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10

7 Copy-on-Write Snapshot troubleshooting . . . . . . . . . . . . . . . . . . . 7-1

General troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2Recovering from failure during pairresync -restore operation . . . . . . . . . . . 7-6Recovering a terminated HP-UX host server . . . . . . . . . . . . . . . . . . . . . . . 7-6Recovering a blocked pool workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6Pool-related SIM entry removal workflow . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

Completing Service Information Messages . . . . . . . . . . . . . . . . . . . . . . 7-7Troubleshooting with Command Control Interface. . . . . . . . . . . . . . . . . . . . . . 7-8

Identifying errors using the log on the CCI window. . . . . . . . . . . . . . . . . 7-15Identifying errors using the Command Control Interface operation log file. 7-16


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A Command Control Interface command reference. . . . . . . . . . . . . . A-1

Command Control Interface commands for Storage Navigator operations . . . . . A-2Storage Navigator and Command Control Interface pair status names . . . . . . . A-2Statuses required for Command Control Interface pair operations . . . . . . . . . . A-2

B Copy-on-Write Snapshot GUI reference . . . . . . . . . . . . . . . . . . . . B-1

Pools window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2Selected pool volume window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6Create Pools wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-15

Create Pools window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-16Confirm window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-21

Expand Pool wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-22Expand Pool window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-22Confirm window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-24

Edit Pools wizard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-25Edit Pools window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-25Confirm window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-27

Delete Pools wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-29Delete Pools window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-29Confirm window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-31

Restore Pools window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-32Complete SIMs window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-33Select Pool window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-34Select Pool Volumes window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-35Pool Property window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-39Create Pairs wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-40

Select Pair Configuration window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-40Select Primary Volumes window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-41

Select Pool window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-45Select Secondary Volumes window . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-46Edit Mirror Units window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-48Confirm window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-49

C Pair operations (secondary window) . . . . . . . . . . . . . . . . . . . . . . C-1

Pair operations workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2Checking pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2Creating a pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

Creating pairs in a consistency group . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

Splitting pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4Resynchronizing pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4Restoring pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5Deleting pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

Deleting a single pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5Deleting multiple pairs related to a port or host group . . . . . . . . . . . . . . . C-5Deleting multiple pairs related to a pool. . . . . . . . . . . . . . . . . . . . . . . . . . C-6


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D Copy-on-Write Snapshot monitoring and maintenance (secondarywindow) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1

Monitoring the system in the secondary window. . . . . . . . . . . . . . . . . . . . . . . D-2Monitoring pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2

Pair status definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3Statuses required for pair operations . . . . . . . . . . . . . . . . . . . . . . . . . . D-3

Monitoring pair volume details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3

Monitoring S-VOL path information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-5Monitoring number of pairs and license information . . . . . . . . . . . . . . . . . D-6Monitoring pair operation history. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-8

Maintaining the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-9

E Copy-on-Write Snapshot GUI reference (secondary window) . . . . . E-1

Pair Operation window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2 Volume list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3Preview list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-5Command menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-6

History window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-6Reference codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-8

C.O.W. Snapshot window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-8

Glossary

Index


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Preface ix


Preface

This guide provides instructions for performing Copy-on-Write Snapshot(SS) tasks on Hitachi Virtual Storage Platform (VSP) storage systems.

Notice: The use of the features and/or software applications described inthis guide and all other Hitachi Data Systems software applications isgoverned by the terms of your agreements with Hitachi Data Systems.

□ Intended audience

□ Product version

□ Document revision level

□ Referenced documents

□ Changes in this revision

□ Document organization

□ Document conventions

□ Convention for storage capacity values

□ Accessing product documentation

□ Getting help

□ Comments


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x Preface

Intended audience

This document is intended for system administrators, Hitachi Data Systemsrepresentatives, and authorized service providers who are involved ininstalling, configuring, and operating the Hitachi Virtual Storage Platformstorage system.

Readers of this document should meet the following requirements:

• Have a background in data processing and understand RAID storagesystems and their basic functions.

• Be familiar with the Hitachi Virtual Storage Platform storage system, andhave read the Hitachi Virtual Storage Platform User and ReferenceGuide.

• Be familiar with the Storage Navigator (SN) software for the HitachiVirtual Storage Platform storage system and have read the HitachiStorage Navigator User Guide.

Product version

This document revision applies to Hitachi Virtual Storage Platformmicrocode 70-06-2 x or later.

You must have Storage Administrator (Local Copy) role to performCompatible FlashCopy® V2 operations in the SN.

Document revision level

Referenced documents

Hitachi Virtual Storage Platform documentation:

• Hitachi Command Control Interface Installation and ConfigurationGuide, MK-90RD7008

Revision Date Description

MK-90RD7013-00 October 2010 Initial release.

MK-90RD7013-01 December 2010 Supersedes and replaces MK-90RD7013-00.

MK-90RD7013-02 April 2011 Supersedes and replaces MK-90RD7013-01.

MK-90RD7013-03 August 2011 Supersedes and replaces MK-90RD7013-02.

MK-90RD7013-04 November 2011 Supersedes and replaces MK-90RD7013-03.

MK-90RD7013-05 March 2012 Supersedes and replaces MK-90RD7013-04.

MK-90RD7013-06 June 2012 Supersedes and replaces MK-90RD7013-05.

MK-90RD7013-07 November 2012 Supersedes and replaces MK-90RD7013-06.

MK-90RD7013-08 January 2013 Supersedes and replaces MK-90RD7013-07.

MK-90RD7013-09 July 2013 Supersedes and replaces MK-90RD7013-08.

MK-90RD7013-10 December 2013 Supersedes and replaces MK-90RD7013-09.

MK-90RD7013-11 September 2014 Supercedes and replaces MK-90RD7013-10


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• Hitachi Command Control Interface User and Reference Guide, MK-90RD7010

• Hitachi Virtual Storage Platform Provisioning Guide for Open Systems,MK-90RD7022

• Hitachi ShadowImage® User Guide, MK-90RD7024

• Hitachi Storage Navigator User Guide, MK-90RD7027

• Hitachi Storage Navigator Messages, MK-90RD7028

• Hitachi Universal Volume Manager User Guide, MK-90RD7032

• Hitachi Virtual Storage Platform User and Reference Guide, MK-90RD7042

Changes in this revision• Added error codes 97D6 and 97D7 to Troubleshooting with Command

Control Interface on page 7-8.

Document organization

The following table provides an overview of the contents and organizationof this document. Click the chapter title in the Chapter column to go to thatchapter. The first page of each chapter provides links to the sections in thatchapter.

Chapter Description

Overview of Copy-on-Write Snapshot on page1-1

Provides an overview of SS.

Copy-on-Write Snapshotplanning and design onpage 2-1

Describes the storage system and operationalrequirements.

Copy-on-Write Snapshotinstallation andconfiguration on page 3-1

Provides instructions for installing and configuring SS.

Sharing Copy-on-WriteSnapshot volumes onpage 4-1

Provides information about sharing SS volumes with otherHitachi Data Systems features and software applications.

Pair operations on page 5-1

Provides instructions for pair operations.

Copy-on-Write Snapshotmonitoring andmaintenance on page 6-1

Provides instructions for monitoring and maintaining pairs.

Copy-on-Write Snapshottroubleshooting on page7-1

Provides troubleshooting information.

Command ControlInterface commandreference on page A-1

Provides command line interface (CLI) commands for SSoperations.


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Document conventions

This document uses the following typographic conventions:

This document uses the icons in the following table to draw attention toinformation:

Copy-on-Write SnapshotGUI reference on page B-1

Describes SS windows and dialog boxes in SN.

Pair operations(secondary window) onpage C-1

Provides instructions for pair operations using the previousSN graphical user interface (GUI), which opens in asecondary window.

Copy-on-Write Snapshotmonitoring andmaintenance (secondarywindow) on page D-1

Provides information for checking status and otherinformation using the previous SN GUI, which opens in asecondary window.

Copy-on-Write SnapshotGUI reference (secondarywindow) on page E-1

Describes SS windows and dialog boxes in the previous SNGUI, which opens in a secondary window.

Chapter Description

Convention DescriptionBold Indicates text on a window or dialog box, including window and

dialog box names, menus, menu options, buttons, items, and

labels. Example: Click OK.

Italic Indicates a variable, which is a placeholder for actual text

provided by the user or system. Example: copy source-file target-file

Note: Angled brackets (< >) are also used to indicatevariables.

screen/code Indicates text that is shown on screen or entered by the user.Example: # pairdisplay -g oradb

< > angled brackets Indicates a variable, which is a placeholder for actual text

provided by the user or system. Example: # pairdisplay -g

Note: Italic font is also used to indicate variables.

[ ] square brackets Indicates optional values. Example: [ a | b ] indicates that you

can choose a, b, or nothing.

{ } braces Indicates required or expected values. Example: { a | b }

indicates that you must choose either a or b.

| vertical bar Indicates that you have a choice between two or more options

or arguments. Examples:

[ a | b ] indicates that you can choose a, b, or nothing.

{ a | b } indicates that you must choose either a or b.

Underline Indicates the default value.

Example: [ a | b]


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Preface xiii


Convention for storage capacity values

Physical storage capacity values (such as disk drive capacity) are calculatedbased on the following values:

Logical storage capacity values (such as logical device capacity) are

calculated based on the following values:

Accessing product documentation

The Hitachi Virtual Storage Platform user documentation is available on theHitachi Data Systems Support Portal: https://portal.hds.com. Please checkthis site for the most current documentation, including important updatesthat may have been made after the release of the product.

Icon Meaning Description

Tip Provides helpful information, guidelines, or suggestions forperforming tasks more effectively.

Note Calls attention to important and/or additional information.

Caution Warns users of adverse conditions and consequences, such asdisruptive operations.

WARNING Warns users of severe conditions and consequences, such as

destructive operations.

Physical capacity unit Value

1 KB 1,000 bytes

1 MB 1,00002 bytes

1 GB 1,0003 bytes

1 TB 1,0004 bytes

1 PB 1,0005 bytes

1 EB 1,0006 bytes

Logical capacity unit Value

1 KB 1,024 bytes

1 MB 1,024 KB or 1,0242 bytes

1 GB 1,024 MB or 1,0243 bytes

1 TB 1,024 GB or 1,0244 bytes

1 PB 1,024 TB or 1,0245 bytes

1 EB 1,024 PB or 1,0246 bytes

1 block 512 bytes

https://hdssupport.hds.com/https://hdssupport.hds.com/


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xiv Preface

Getting help

The Hitachi Data Systems customer support staff is available 24 hours aday, seven days a week. If you need technical support, log on to the HitachiData Systems Support Portal for contact information:https://portal.hds.com.

Comments

Please send us your comments on this document:[email protected]. Include the document title, number, and revision,and refer to specific sections and paragraphs whenever possible. Allcomments become the property of Hitachi Data Systems.

Thank you!

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1

Overview of Copy-on-Write Snapshot 1–1


Overview of Copy-on-Write Snapshot

With Copy-on-Write Snapshot (SS), you can create virtual copies of a datavolume in the Hitachi Virtual Storage Platform storage system.

This chapter provides instructions for planning and designing, configuring,operating, monitoring, and troubleshooting SS.

□ Copy-on-Write Snapshot software

□ How Copy-on-Write Snapshot works

□ Components

□ Licenses and capacity

□ Consistency groups

□ Interfaces for performing Copy-on-Write Snapshot operations

□ Pair status


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1–2 Overview of Copy-on-Write Snapshot

Copy-on-Write Snapshot software

SS creates a virtual, point-in-time copy, or snapshot, of a data volume.Since only changed data blocks are stored in the SS storage pool, storagecapacity is substantially less than the source volume. This results insignificant savings compared with full cloning methods.

The most probable types of target applications for SS are:

• Database copies for decision support and database inquiries.• Non-disruptive backups from an SS secondary volume (S-VOL).

• Periodic point-in-time disk copies for rapid restores in the event of acorrupted data volume.

How Copy-on-Write Snapshot works

You create a volume pair when you complete the following:

1. Select the volume that you want to replicate.

2. Identify another volume that will contain the copy.

3. Associate the primary volume (P-VOL) and S-VOLs.4. Set up a data pool.

5. Create the pair.

The P-VOL is updated. The virtual volume (V-VOL) points to the point-in-time data in the P-VOL and data pool and mirrors it. The V-VOLcontains a virtual copy of the P-VOL; it does not contain actual data.

For more information about creating pairs, see Pair creation on page 5-3.

6. Split the pair.

The storage system continues to update the P-VOL. The V-VOL stops

mirroring the current P-VOL. Instead, the V-VOL maintains a snapshotfrom the time of the split.

For more information about splitting pairs, see Pair split on page 5-9.

7. Write data to the P-VOL.

SS maintains the point-in-time image by copying the existing data to thedata pool.

8. Resume the pair.

The pool data is deleted.

Volume pairs: P-VOLs and V-VOLs

A volume pair consists of a P-VOL, which contains the original and actualdata, and at least one and up to 64 V-VOLs. The V-VOL is made up ofpointers to the data in the P-VOL. The P-VOL and its V-VOLs are located inthe same storage system. A V-VOL is also referred to as an S-VOL.

Although you must set up V-VOLs with the same capacity as the paired P-VOL, the capacity is not actually used and remains available as free storagecapacity. This V-VOL sizing requirement is necessary for SS and the storage


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system logic. The V-VOL pointers to data in the data pool and P-VOL residein cache memory. Enabling your system’s cache reserves part of yoursystem’s cache for SS.

Splitting the volume pair moves the original data to the data pool as the P-VOL is updated. The following figures show SS volumes and data poolinteraction when you split the pair.

The following figure shows how the V-VOL maintains the point-in-time data

when you split the pair.

The following figure shows how the V-VOL maintains the point-in-time datawhen you split the pair.

The following image shows how the V-VOL maintains point-in-time data

when you split the pair.


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Data pools

When you replace data in the P-VOL, the data pool holds the data. After yousplit a pair, the V-VOL maintains pointers to point-in-time data. If updatesare written to the P-VOL before you update the block, the data that is beingreplaced is first copied to the data pool. The V-VOL pointer to this block isupdated to the new address in the data pool. All pairs sharing the same P-VOL use a data pool.

Components

An SS system typically consists of the following components:

• The SN

• SS and ShadowImage (SI) software

• Command Control Interface (CCI)

• A pair of volumes (P-VOL and S-VOL)

• A data pool

• A consistency group

Licenses and capacity

To use SS, SI must be installed on the same system. You must providesufficient licensed capacity for both SS and SI.

SS uses a V-VOL management area for managing V-VOLs and data pools.The V-VOL management area is created when additional shared memory isinstalled.

The V-VOL management area consists of the following:

• Pool management block

• Pool association information


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The following table shows the volumes and capacities for calculating theusable capacity for SS. The total applicable capacity must be less than thecapacity you have licensed for SS. If you need more licensed capacity, callthe Support Center.

Related topics

• Calculating maximum SS pairs based on shared memory workflow onpage 2-9.

Consistency groups

Define SS pair operations in consistency groups to perform the operationson multiple pairs at the same time. Set up consistency groups during paircreation.

For more information about creating pairs, see Pair creation on page 5-3.

Interfaces for performing Copy-on-Write Snapshotoperations

You perform setup and pair operations using a combination of the following:

• The SN. For more information about the SN, see The Storage Navigatoron page 1-5.

• Command Control Interface (CCI). For more information about CCI, seeCommand Control Interface on page 1-6.

The Storage Navigator

The Storage Navigator (SN) is connected to the Hitachi Virtual StoragePlatform storage system through the TCP/IP local-area network (LAN). TheSN communicates and exchanges data directly with the service processor(SVP) of the connected storage system.

Use the SN to do the following:

• Create the data pools and V-VOLs. For more information:

About creating data pools, see Creating data pools on page 3-2.

About creating V-VOLS, see Creating V-VOLs on page 3-4.

• View pair and data pool status. For more information:

Volumes to be added Applicable

capacitySoftware Volume typeNormal VOL or

DP-VOL

SS P-VOL Normal VOL Volume capacity

DP-VOL Pool capacity usedby the volume

Pool volume (pool-VOL)

Normal VOL Volume capacity


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About viewing pair status, see Monitoring pair information, licensecapacity, status on page 6-2.

About viewing data pool status, see Monitoring pool information onpage 6-5.

Command Control Interface

Use CCI to perform pair operations. CCI is set up on the host server. SS

commands are sent from CCI to a command device on the storage systemand is volume dedicated to CCI communications. Other Hitachi DataSystems software applications cannot use this volume.

Pair status

The status of a pair is an indicator of its condition. You check the status tosee when an operation is completed or when an operation can be done. Formore information about monitoring pair information, license capacity, andstatus, see Monitoring pair information, license capacity, status on page 6-2.


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2

Copy-on-Write Snapshot planning and design 2–1


Copy-on-Write Snapshot planning anddesign

This chapter describes requirements for setting up and using SS andincludes data pool sizing information.

□ Consistency group system requirements

□ Data pool requirements and restrictions

□ Planning pair volumes

□ Calculating the number of Copy-on-Write Snapshot pairs

□ Planning for splitting pairs in consistency groups

□ External volumes


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2–2 Copy-on-Write Snapshot planning and design

Consistency group system requirements

The following table includes a list of consistency group systemrequirements.

Note: Many of these requirements are augmented with restrictions.

Item Requirement

Software SI is required to operate SS. Install and enable the VirtualStorage Platform (VSP) storage system hardware,microcode, and software required for SI operations.

License capacity Consider the capacity of the volume when purchasinglicensed capacity. Capacity for SS is part of the licensedcapacity for SI. Ensure that the licensed capacity for SI ismore than the combined capacity needed for bothsoftware applications.

The number of software applications using a volume doesnot increase the amount of licensed capacity that youmust purchase.

Shared memory Required:

• SS/VFS1: 716.8 MB (RACK model is supported up toVFS1.)

• SS/VFS2: 1,021 MB (VFS1 + 307 MB)

• SS/VFS3: 2,045 MB (VFS1,2 + 1024 MB)

• SS/Extension 1: 4,096 MB (SS/VFS1 + 3379.2 MB)

VSP storage systems can handle a 7.15 TB database withseven generations.

Verify that your system is installed with the appropriate

SS V-VOL management area.

Restriction:

• You cannot share the V-VOL management areamemory with Dynamic Provisioning (HDP).

CCI CCI is required for you to perform SS pair operations. CCIrequires that you use one volume as a command device.

For more information about setting up the CCI, see theHitachi Command Control Interface Command Reference.


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Volume type The P-VOL, V-VOL, and volumes must be logical volumes(LDEVs).

For more information about volume type, see thefollowing:

• Data pool requirements and restrictions on page 2-4

• External volumes on page 2-16

To maintain performance levels, use the followingconfigurations:

• Do not mix normal volumes and data pool-VOLs in thesame parity group.

• Ensure that the data pool-VOLs consist of LDEVs frommultiple parity groups.

• Assign different processor blade identifiers to LDEVsthat make up data pool-VOLs.

For more information about assigning the processorblade identifier, see the Hitachi Virtual StoragePlatform Provisioning Guide for Open Systems.

Emulation type (For P-VOL, V-VOL, and data pool-VOLs) OPEN-V

Pair configuration V-VOL limit per P-VOL: 64

RAID level Supported: RAID1, RAID1+0, RAID5, and RAID6

Restriction: You cannot add a different RAID level to thedata pool.

LUSE Supported: P-VOL and V-VOL

Not supported: pool-VOL

CLPR The data pool must contain pool-VOLs belonging to thesame cache logical partition.

Number of P-VOLs and V-VOLs

P-VOL: 16,384

V-VOL: 16,384

For more information about calculating the number of SSpairs, see Calculating the number of Copy-on-Write

Snapshot pairs on page 2-7.

Maximum number of data

pools

128

(HDP, Dynamic Tiering (HDT), and Dynamic Provisioningfor Mainframe (HDPz) pools) Creating pools for HDP, HDT,and HDPz reduces the number of usable pools for SS.

Pool-VOL capacity 8 GB to 4 TB

Maximum number of pool-VOLs in a data pool

1,024

Restriction: You cannot register volumes that are

already registered in a pool as pool-VOLs to another pool.

Expansion of data pool-VOLcapacity Allowed, even if snapshots are using the pool.

Deletion of data pool Allowed. You must first use the pool to delete the pairs.

For more information about deleting pairs, see Deletingpairs on page 5-12.

Item Requirement


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Data pool requirements and restrictions

To use a volume as a data pool, the volume’s LDEV status must be “Normal”or “Normal (Quick Format)”.

You cannot use the following volumes as data pools:

• LUSE or Cache Residency Manager (CRM) volumes, system disks,command devices, quorum disks.

• Volumes in “Block” status or volumes in copying process.

• SS P-VOLs or V-VOLs.

Use of external volumes inpool

Allowed.

For more information about external volumes, seeExternal volumes on page 2-16.

Data drive type SAS, SATA, and SSD

(Internal and external volumes) You can use pool-VOLswith different drive types in the same pool.

For optimum performance, use volumes with the samedrive types.

Operating systemrestrictions

(For HP-UX host servers only)

Restriction: Create the SS pair before running thecommand for recognizing the device or V-VOL on the hostserver.

Important! Do not use a volume already recognized bythe host server as a V-VOL. If you do, an error can occurand the HP-UX host server can terminate.

For more information about recovering terminated HP-UX

host servers, see Recovering a terminated HP-UX hostserver on page 7-6.

Consistency groups (CG) The consistency group number. You define this numberduring the paircreate command.

Note: If you do not specify a number, an unused numberis assigned.

Values: 128-255 (80 to FF).

Maximum number of SS pairs per CG: 8,192

Maximum number of CGs per storage system: 256including SI and ShadowImage for Mainframe (SIz) CGs.

Restrictions:

• Do not combine pairs with the same P-VOL in thesame CG.

• Do not combine SI, SIz, and SS pairs in the same CG.

For more information about consistency groups, see theHitachi Command Control Interface User and ReferenceGuide.

For more information about creating pairs using thepaircreate command, see Creating pairs in aconsistency group on page C-3.

Item Requirement


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• Volumes which are already being used as data pools for SS or HDP(including HDT).

• Volumes used by another software application pair or migration plan.

• Volumes with Protect or Read Only attribute, or the S-VOL Disable setting.

The following are rules and restrictions regarding volumes:

• You cannot use external and internal volume pool-VOLs in the same datapool.

• You must use the same pool for all pairs sharing the same P-VOL. Forexample, if you pair one P-VOL with three V-VOLs, the three pairs mustuse the same data pool.

• You cannot use volumes that are in the different resource groups in thesame data pool.

Planning pair volumes

You must set up the pair volumes and data pools before creating the pair.

For more information about planning pair volumes, see the following:

• Planning V-VOLs and data pools on page 2-5

Sizing the data pool workflow on page 2-6

Planning V-VOLs and data pools

When you plan an SS implementation, keep the following considerations inmind:

• The frequency in which you will create snapshots of the P-VOL.

• The lifespan for each snapshot (V-VOL).

• The number of snapshots (V-VOLs) you will create and the V-VOL limitper P-VOL.

For more information about the V-VOL limit per P-VOL, see Consistencygroup system requirements on page 2-2.

Use copy frequency and V-VOL lifespan to determine the number of V-VOLs your system requires per P-VOL.

For example: If your data must be copied every 12 hours, and businessuse of the V-VOL requires holding it 48 hours, set up four V-VOLs.

• The size of the data pool. Copy frequency, V-VOL lifespan, and thenumber of V-VOLs are factors in determining data pool size. The moretime that elapses between snapshots, the longer a snapshot is held, andthe more snapshots that exist all result in more data accumulating in thedata pool.

Note: Set the access attributes using the Data Retention Utility(DRU).

For more information about setting the access attributes, see The DataRetention Utility and access attributes on page 4-3.


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For more information about data pool sizing, see Sizing the data poolworkflow on page 2-6.

Sizing the data pool workflow

Updating the P-VOL replaces and holds the P-VOL data in the data pool. Theoriginal data in the data pool is held to maintain the image of the P-VOL at

the time of the snapshot.

To determine the size of the data pool, do the following:

1. Measure write workload over time from the host software application tothe P-VOL. Write workload is the megabytes-per-second that are writtento the P-VOL over a specific amount of time.

2. Calculate the amount of data that would accumulate during the lifespanof your V-VOLs.

3. Multiply the amount of data that accumulates by the number of V-VOLs.

The following figure shows the basic factors for data pool sizing.

When you finalize the capacity for a data pool, factor in the following:

• A safety factor of 20 percent. Having a safety factor calculated inminimizes the chances of over-filling the data pool. To factor in a safetyfactor of 20 percent, multiply the base data pool size by 1.2.

• Annual increase in data transactions. Your business data is likely togrow. Multiply the base pool size by the percentage of expected annualgrowth.


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• The unit size of 256 KB. Data is copied to a pool in units of 256 KB. Thisis true even when the actual write data is smaller than 256 KB. In sucha case, the write consumes 256 KB of the pool-VOL capacity.

Calculating the number of Copy-on-Write Snapshot pairs

The available system resources for copying pairs limits the number of SSpairs that you can create in the storage system. Confirm with your service

provider that additional shared memory for differential tables and the V-VOLmanagement area are installed on your system.

The maximum number of SS pairs supported on a system is the lowestvalue based on the following calculations:

• The number of differential tables.

For more information about calculating based on differential tables, seeCalculating maximum SS pairs based on differential tables workflow onpage 2-7.

• The shared memory capacity for the V-VOL management area.

For more information about calculating based on shared memory, see

Calculating maximum SS pairs based on shared memory workflow onpage 2-9.

• Number of pair tables.

For more information about calculating based on pair tables, seeCalculating maximum pairs based on pair tables on page 2-12.

If you are creating external volumes or Thin Image (HTI), HDP, or HDT V-VOLs in the storage system, see Calculating SS pairs when creating externalvolumes or V-VOLs on page 2-7.

Calculating SS pairs when creating external volumes or V-VOLs

If you are creating external volumes or HTI, HDP, or HDT V-VOLs in thestorage system, the maximum number of SS pairs you can create is thelowest value based on the following calculations and no more than 63,232pairs:

• The value of the calculations for calculating the number of SS pairs.

For more information about calculating the number of SS pairs, seeCalculating the number of Copy-on-Write Snapshot pairs on page 2-7.

• Max. num. SS pairs = Num. of external volumes + Num. of HTI,HDP, HDT, and SS V-VOLs

Calculating maximum SS pairs based on differential tablesworkflow

Differential tables keep track of the updates that take place in pairs. Thenumber of these tables a pair requires depends on the size of the volumes.


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A base that does not have shared memory has 26,176 differential tables.The remaining number of differential tables on a system is determined bythe amount of shared memory that is installed on your system. For moreinformation about determining this amount, see Determining maximumpairs allowed on your system on page 2-12.

When you use SS, the shared memory level is COW 1 with Extension 1 andExtension 2. The following table shows the shared memory levelcombinations and the number of differential tables that are associated with

them.

The following software applications also use differential tables:

• SI

• SIz

• Compatible FlashCopy® V2

• Volume Migration

Using differential tables, use the following workflow to find the maximumnumber of pairs allowed on your system:

1. The number of differential tables required for each pair.

2. The maximum number of pairs your system supports based on thenumber of differential tables in the storage system. To calculate thenumber of differential tables that are unused and available for SS pairson the storage system, use the following calculation:

(The number of differential tables used by all other softwareapplications on the storage system) - (The total number ofdifferential tables that are available on the storage system)

1. Calculate the number of differential tables required for one SSpair (O) using the following formula:

where:

X = Capacity of the volume in kilobytes.

Z = Number of slots that a differential table can manage (639 × 32).

Round up to the nearest whole number.

Example:

Combination Differential tables required

Base with no shared memory 26,176 tables

Extension 1 104,768 tables

Extension 2 209,600 tables

Note: “ceil” indicates that you must round up the result within theparenthesis () that follows.

ceil((X ÷ 256) ÷ Z)


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In this example, you must create four differential tables to create one SSpair.

2. Calculate the maximum number of SS pairs using the followingformula:

where:

T = Total number of differential tables.

D = Number of differential tables required for one SS pair.

M = Maximum number of SS pairs.

Example: This example assumes that no other software application is usingdifferential tables, and that the number of differential tables is 57,600.

In this example, the maximum number of pairs allowed for SS is 14,400pairs.

On the example system, you can create a maximum of 6,544 SS pairs basedon differential tables.

Calculating maximum SS pairs based on shared memory workflow

Shared memory capacity for the V-VOL management area depends on

additional shared memory. You can check the pool management block andpool association shared memory capacity in the C.O.W. Snapshot window.

For more information about this window, see C.O.W. Snapshot window onpage E-8.

The following table shows a system’s shared memory capacity based on theamount of additional shared memory. This table also shows the V-VOLmanagement area’s memory capacity.

You can calculate the maximum number of SS pairs that you can createbased on the amount of additional shared memory in the V-VOLmanagement area.

Use the following workflow to calculate the maximum number of pairs:

(16,777,216 kB ÷ 256) ÷ (639 x 32)= 3.19523, which rounds up tofour.

T ÷ D = M

576,00 ÷ 4 = 14,400

Note: For an SS pair, one pair consists of a P-VOL and up to 64 V-VOLs.Generations of snapshots do not apply when you perform differential tablecalculations.

Shared memory Shared memory capacity

SS 751,619,276 bytes

SS Extension 1 4,294,967,296 bytes


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1. Calculate the capacity of the pool management block, which is the totalcapacity of shared memory used by the pool-VOL (see Calculate thecapacity of the pool management block on page 2-11).

2. Calculate the capacity of pool association information, which is the totalcapacity of shared memory used by the P-VOL (see Capacity of poolassociation information on page 2-12).

Example

This example assumes the following:

• The V-VOL management area’s shared memory has a capacity of 716 MB(751,619,276 bytes).

• There are four pool-VOL pools, each having a capacity of 1 TB(1,073,741,824 KB).

• Each P-VOL has a capacity of 10 GB (10,485,760 KB).Use the following formula to calculate the maximum number of SS pairs (P-VOLs) you can create in a storage system:

Using these examples, the maximum number supported based on additionalshared memory in the V-VOL management area is 1,136 pairs.

The following table shows the pool capacity for shared memory and the P-VOL capacity that you can create.

Note: ceil in the formulas indicates that you must round up the resultwithin the parenthesis () that follows.

floor in the formulas indicates that you must round down the result withinthe parenthesis () that follows.

The capacity (bytes) of shared memory used by the pool-VOL =ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640) X 8,736 +ceil (ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640) X8,736 +ceil (ceil (ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640)X 8,736= 135,713,760 + 69,888 + 8,736= 135,792,384 (bytes)The capacity of the pool management block = 135,792,384 X 4= 543,169,536 bytes

The capacity (bytes) of shared memory used by the P-VOL =ceil (ceil (10,485,760 (KB)/256 (KB))/2,048) X 8,736 +ceil (ceil (ceil (10,485,760 (KB)/256 (KB))/2,048) X 8,736= 17,472 +8,736= 26,208 (bytes)Maximum number of SS pairs (P-VOLs) = (751,619,276 - 543,169,536)/ 183,456= 208,449,740 / 183,456= 1,136

Sharedmemory

Pool capacity (GB)

2,048 4,096 6,144 8,19210,24

012,28

814,33

620,48

030,720

SS 26(TB)

11(TB)

- - - - - - -


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The total capacity of pool-VOLs registered in a pool is the capacity of thatpool. The capacity of the pool you want to create depends on the sharedmemory extension status.

The following graph roughly shows the relationship between the allowablepool capacity and the P-VOL capacity depending on the shared memoryextension status.

Calculate the capacity of the pool management block

The capacity of the pool management block is the total capacity of sharedmemory used by the pool-VOL.

Use the following formula to calculate the capacity:

Copy capacity and creating pools

Estimate the copy capacity (the capacity of SS data to be copied to the pool)and then set the pool capacity large enough to accommodate the copycapacity. If the copy capacity varies according to time, use the maximumcopy capacity in your calculation. Creating a pool when the pool capacity isinsufficient can suspend the SS pairs (“PSUE” status).

SSExtension1

224(TB)

209(TB)

194(TB)

179(TB)

163(TB)

148(TB)

133(TB)

88(TB)

12

(TB)

Sharedmemory

Pool capacity (GB)

2,048 4,096 6,144 8,19210,24

012,28

814,33

620,48

030,720

Capacity (bytes) of shared memory used by the pool-VOL =ceil (floor (pool-VOL capacity (KB)/256 (KB)) X 32/8,640)X 8,736 + ceil (ceil (floor (pool-VOL capacity (KB)/256 (KB))X 32/8,640)/2,048) X 8,736 +ceil (ceil (ceil (P-VOL capacity (KB)/256 (KB))X 32/8,640)/2,048)/1,024) X 8,736


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Pool capacity and copying SS data

Copying SS data to the pool consumes the pool capacity in units of 256 KB.You must allow for this amount of pool capacity even in situations where lessthan that amount is consumed.

Capacity of pool association information

The capacity of the pool association information is the total capacity of

shared memory used by the P-VOL.

Use the following formula to calculate the capacity:

Calculating maximum pairs based on pair tables

SS and Compatible FlashCopy® V2 (FCv2) pairs use pair tables. A pair tablekeeps track of the status for a pair. You use one pair table for each pair.

To calculate the maximum number of SS pairs you can create, use thefollowing formula:

Max. num. SS pairs = The number of pair tables - The number ofFCv2 pairs on the storage system

A storage system contains 1,048,575 pair tables. On the example system,you can create a maximum of 1,048,575 SS pairs based on pair tables.

Determining maximum pairs allowed on your system

To determine the maximum number of SS pairs your system supports, usethe example calculations described in the following sections:

• Calculating maximum SS pairs based on differential tables workflow onpage 2-7.

• Calculating maximum SS pairs based on shared memory workflow onpage 2-9.

• Calculating maximum pairs based on pair tables on page 2-12.

Planning for splitting pairs in consistency groups

At-Time Split to split pairs in a consistency group at a pre-determined time.You can At-Time Split multiple pairs and multiple pairs whose P-VOLs areshared with TrueCopy (TC) or Universal Replicator (UR) S-VOLs.

Use the following list to plan for splitting pairs in consistency groups:

1. Note the requirements in Requirements and restrictions for the At-TimeSplit operation on page 2-13.

2. Before defining consistency groups for the pairsplit operation, read theinformation in Pair inclusion in At-Time Split operations workflow onpage 2-13.

Capacity (bytes) of shared memory used by the P-VOL =ceil (ceil (P-VOL capacity (KB)/256 (KB))/2,048) X 8,736+ ceil (ceil (ceil (P-VOL capacity (KB)/256 (KB))/2,048)/1,024)X 8,736


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3. To share SS P-VOLs with UR or TC S-VOLs within a storage system, readthe information in Consistency maintenance workflow when sharing SSP-VOLs with UR or TC volumes on page 2-14.

Requirements and restrictions for the At-Time Split operation

Note the following requirements and restrictions when setting up to performan At-Time Split operation:

• You must include the pairs in the same consistency group.

• The pairs must have a status of “PAIR”. For more information about pairstatus, see Pair status definitions on page 6-2.

• If you want to make changes to the pair, make the change in the sameconsistency group according to the copy group.

• Registering the At-Time Split operation:

You can split or delete pairs while registering the At-Time Split. If youcreate a pair, split a pair, or resynchronize a pair, the split time isrejected. To perform one of these operations, reset the registrationof the At-Time Split.

Switching off the power resets the pre-determined split time. Performs the At-Time Split operation when a read/write

request—with a time stamp past the specified Split time—is received.Run a read/write request to prevent delays in the Split operation.When I/O does not occur, the storage system timer performs theSplit operation.

If the split operation fails, the status all volumes in the consistencygroup remains the same as before the At-Time Split operation.

• If the consistency group contains a pair whose status cannot bechanged, the pairsplit command can terminate abnormally (with errorcode EX-EWSTOT (Timeout)). The following are possible reasons:

The SS P-VOL is also used as an UR S-VOL and the UR journalcapacity is insufficient.

The SS license is invalid.

An SS pair volume is blocked.

The SS pair has a status that does not allow you to perform thepairsplit operation.

For more information about SS pair status, see Statuses required forCommand Control Interface pair operations on page A-2.

The SS pair has a status that does not allow UR to run the pairsplit command.

Pair inclusion in At-Time Split operations workflow

Use the following workflow to include pairs in an At-Time Split operation:

1. Review the requirements for consistency groups in Consistency groupsystem requirements on page 2-2.


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2. Place the pairs in a consistency group. Specify only one consistencygroup for a group defined in the CCI configuration file.

Consistency maintenance workflow when sharing SS P-VOLs withUR or TC volumes

Use the following workflow to share SS P-VOLs with UR or TC S-VOLs withina storage system and to maintain consistency:

1. Place the SS pairs in a consistency group.

2. Split the pair in a consistency group.

For more information about splitting pairs in consistency groups, seeSplitting pairs in consistency groups at a pre-determined time on page5-10.

The following figure shows the At-Time Split configuration with UR.

Note: Performing the pairsplit operation when the pairs are placed ina consistency group does not guarantee the acquired snapshot data tobe the P-VOL data.

To guarantee that the acquired snapshot data is the P-VOL data, includepairs that do not share the same P-VOL in the consistency group.

To avoid a pairsplit operation failure, include only pairs that are inconsistency groups in a group (not a consistency group) that you havedefined in the CCI configuration file. When creating a pair using a groupthat you defined in the CCI configuration file, if another pair in the groupis part of a consistency group, place the pair you are creating in thesame consistency group. If you want to specify multiple consistencygroups, define a group for each consistency group.

To avoid a command rejection and a generating a consistency groupnumber that does not include the SS pair, create a pair for an At-TimeSplit operation when the host server is running. If the host server isdown, create the pair using the consistency number. In the SN, use the

Consistency Groups tab in the Local Replications window.

For more information about creating pairs using the paircreate command, see Creating pairs in a consistency group on page C-3.


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The following figure shows the At-Time Split configuration with TC.


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Snapshot secondary volume consistency maintenance

If you are sharing the SS P-VOL with one of the following S-VOLs, ensurethe following to maintain SS S-VOL consistency:

• (SI, TC, and/or UR) The pair status must be the same.

For more information: About sharing SI P-VOLs and S-VOLs with SS P-VOLs, see

ShadowImage on page 4-5.

About sharing TC and/or UR pair volumes with SS P-VOL, seeTrueCopy and Universal Replicator on page 4-7.

• (UR) The journal group must be the same.

For more information about sharing UR pair volumes with SS P-VOLs,see TrueCopy and Universal Replicator on page 4-7.

For more information about sharing Hitachi Data Systems softwareapplication volumes with SS P-VOL and S-VOLs, see Interoperability with

other software applications and functions on page 4-2.

External volumes

External volumes are volumes on external systems. You can connectmultiple external storage systems to a VSP storage system. You can useexternal volumes as pool-VOLs, but this blocks the pool-VOLS and the pool.


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External-volume failures

To minimize the effects of the external-volume failure, specify one kind ofvolume as data pool-VOLs in a particular pool, either internal volumes orexternal volumes.

For more information about external systems and the solutions for theerrors related to external volumes, see the Hitachi Universal VolumeManager User Guide.


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3

Copy-on-Write Snapshot installation and configuration 3–1


Copy-on-Write Snapshot installationand configuration

This chapter provides instructions and information for installing andconfiguring SS.

□ Installing and removing Copy-on-Write Snapshot

□ Configuration workflow

□ Creating data pools

□ Creating V-VOLs

□ Setting up the Command Control Interface command device


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3–2 Copy-on-Write Snapshot installation and configuration

Installing and removing Copy-on-Write Snapshot1. In the SN, install SI.

2. Install the SS license key.

To remove SS, complete the following:

1. Delete the SS pairs, pools, and V-VOLs.

For more information about deleting SS pairs, pools, and V-VOLs, see:

Deleting pairs on page 5-12.

Deleting pool volumes on page 6-8.

Deleting virtual volumes on page 6-9.

2. In the SN, remove SS.

Configuration workflow

Use the following workflow to set up SS:

1. Create the data pool.

For more information, see Creating data pools on page 3-2.2. Create the V-VOL.

For more information, see Creating V-VOLs on page 3-4.

3. (Optional) Set up the CCI command device.

For more information, see Setting up the Command Control Interfacecommand device on page 3-5.

Creating data pools

Splitting the pair replaces data in the P-VOL and stores data in the datapool. The V-VOL maintains a point-in-time image.

To create data pools, use the Create Pools window. Define the requireditems, as indicated with an asterisk (*). From this window, you can createthe data pool and then continue to the next page where you can createLDEVs for the pools.

Size the pool according to the write workload and within the range for pool-VOL capacity.

For more information about sizing data pools, see Sizing the data poolworkflow on page 2-6.

For more information about the pool-VOL capacity, see Consistency group

system requirements on page 2-2.

Prerequisite information

• Before creating the data pool, determine what is needed to assign pool-VOLs.


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• For more information about consistency group system and data poolrequirements, see Consistency group system requirements on page 2-2 and Data pool requirements and restrictions on page 2-4.

1. In the Storage Systems tree, select Pools > Create Pools.

2. In the Create Pools window, for Pool Type, select COW Snapshot.

3. In the Pool Volume Selection area of the Create Pools window,complete the following items:

For Drive Type/RPM, select your system’s data drive type and RPM.

Values:

- Mixable

- External Storage

For RAID Level, select your system’s RAID level.

4. In the Pool Volume Selection area of the Create Pools window, clickSelect Pool VOLs, and complete the following:

a. In the Select Pool Volumes window, in the Available PoolVolumes table, select the pool-VOLs you want and click Add.

b. Complete the following and then click OK:

- To select all pool-VOLs in the list, click Select All Pages.

- To filter the rows, for Filter, click ON.

- To specify the number of rows to show, click Options and make theselection.

- To select pool-VOLs, select the pool-VOL from the Available PoolVolumes table and move it to the Selected Pool Volumes table.

5. In the Create Pools window, for Pool Name, type a name for the pooland then click Options.

6. In the Options area of the Create Pools window, complete thefollowing items and then click Add:

For Initial Pool ID, enter a number.

For Warning Threshold, select a data pool capacity threshold.

The new pool is added to the Selected Pools table.

7. Click Finish.

Caution: You cannot delete pool-VOLs that you have added. Before addingthe pool-VOL, ensure that the pool-VOL settings are correct.

Note: For item descriptions, including character limits, see Create Pools

window on page B-16.

Note: If you select External Storage as the drive type/RPM, asingle dash (-) is shown as the RAID level, which indicates that youcannot select the RAID level.

Note: To create the data pool and then continue to the next pagewhere you can create LDEVs for the pools, click Next.


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8. In the Confirm window, click Apply.

The data pool is created.

Creating V-VOLs

For more information about V-VOLs and P-VOLs, see Volume pairs: P-VOLsand V-VOLs on page 1-2.

Prerequisite Information

• The data pool must exist.

For more information about creating data pools, see Creating data poolson page 3-2.

• The V-VOL must be the same size as the P-VOL.

• The V-VOL recognized by the host server must have a status of “PSUS”.

• You can create a maximum of 64 V-VOLs per P-VOL.

• For HP-UX/Solaris and other operating systems: Do not use a volumethat is already recognized by the host server as a V-VOL. For moreinformation about the HP-UX host servers operating system restrictions

and the V-VOL requirements, see Consistency group systemrequirements on page 2-2.

For more information about determining how many V-VOLs you mustcreate, how long to hold an SS, and other planning considerations, seePlanning V-VOLs and data pools on page 2-5.

1. In the Storage Systems tree, select Logical Devices > LDEVs >Create LDEVs.

2. On the Create LDEVs window of the Create LDEVs wizard, forProvisioning Type, confirm that COW Snapshot is selected.

3. Complete the following items:

For System Type, confirm OPEN is selected.

For Emulation Type, confirm OPEN-V is selected.

For LDEV Capacity, type the capacity for the new V-VOL.

Enter the capacity within the range of figures shown below the textbox. Enter the number with two digits after the decimal point.

For Number of LDEVs, type the number of V-VOLs (LDEVs) youwant to create.

For LDEV Name, type a name for the new V-VOL.

For Prefix, type alphanumeric characters.

Case-sensitive: Yes

For Initial Number, type a number.

Limit: 9 digits

Character limit: 32

Note: For item descriptions, including character limits, see Copy-on-WriteSnapshot GUI reference on page B-1.


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4. Click Option and complete the following items and then click Add:

For Initial LDEV ID, ensure that the LDEV ID is set.

To confirm the used number and unavailable number, click ViewLDEV IDs, which opens the View LDEV IDs window.

For Initial SSID, enter the (storage) subsystem identifier (SSID).

Characters/digits: 4-digit representation of a hexadecimal number

Values: 0004 to FFFE

To confirm the created SSID, click View SSID to open the ViewSSID windows.

For Cache Partition, select the CLPR .

For Processor Blade, assign a processor blade. To assign a specificprocessor blade, click the ID for the processor blade. To assign thenext available processor blade, click Auto.

The new V-VOLs are added to the Selected LDEVs table.

5. Do one of the following:

To open the next page where you can create LDEVs, click Next toopen the Create LDEVs window.

To confirm this operation, click Finish.

6. In the Confirm window, do the following and then click Apply:

For Task Name type a name for the task.

For Go to tasks window for status, select to open the Tasks window.

More information

• For more information about the tasks you can perform using the CreateLDEVs wizard and window, see the Hitachi Virtual Storage PlatformProvisioning Guide for Open Systems.

• For more information about creating LDEVs and about the tasks you canperform from this window, see the Hitachi Virtual Storage PlatformProvisioning Guide for Open Systems.

Setting up the Command Control Interface commanddevice

You must set up a volume on the storage system for the CCI and dedicateit as the CCI command device. This device acts as the interface between theCCI and the storage system.

For more information about how to set up the command device, see theHitachi Command Control Interface Command Reference.

Caution: You cannot change the LDEV ID. It is automaticallyregistered.

Note: For character and symbol limits and default values, seeComplete SIMs window on page B-33.


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4

Sharing Copy-on-Write Snapshot volumes 4–1


Sharing Copy-on-Write Snapshotvolumes

This chapter discusses the Hitachi Data Systems software applicationvolumes that you can share with SS P-VOLs.

□ Interoperability with other software applications and functions

□ The Data Retention Utility and access attributes

□ Dynamic Provisioning

□ Resource Partition Manager

□ ShadowImage

□ TrueCopy and Universal Replicator

□ Volume Migration

□ Thin Image


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4–2 Sharing Copy-on-Write Snapshot volumes

Interoperability with other software applications andfunctions

You can share the following Hitachi Data Systems software applicationvolumes with SS P-VOLs:

• Dynamic Provisioning

For more information about sharing volumes with HDP, see Dynamic

Provisioning on page 4-4.• Resource Partition Manager

For more information about sharing volumes with Res Par, see ResourcePartition Manager on page 4-5.

• ShadowImage

or more information about sharing volumes with SI, see ShadowImageon page 4-5.

• TrueCopy and Universal Replicator

For more information about sharing volumes with TC and UR, seeTrueCopy and Universal Replicator on page 4-7

• Volume Migration

For more information about sharing volumes with Volume Migration, seeVolume Migration on page 4-9.

• Thin Image

For more information about sharing volumes with HTI, see Thin Imageon page 4-9.

Use the following table to determine the interoperability of other HDSsoftware applications and function volumes with SS P-VOL and S-VOLs.

Software application and function

volume typesUsed as SS P-VOL Used as SS S-VOL

HTI P-VOL No No

HTI S-VOL No No

SI P-VOL Yes No

SI S-VOL Yes No

TC P-VOL Yes No

TC S-VOL Yes No

UR P-VOL Yes No

UR S-VOL Yes No

Volume Migration source volume Yes No

Volume Migration target volume No No

Read Only volume Yes Yes

Protect volume Yes Yes

“S-VOL Disable” volume Yes Yes

Zero Read Capacity volume Yes Yes

Invisible volume Yes Yes


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The Data Retention Utility and access attributes

The SS pair and pool operations that you can perform for volumes dependon the access attributes that you set. Set the access attributes using the SN

DRU.

You can also set SS pair P-VOLs and S-VOLs access attributes and reservevolumes.

The following table shows the SS pair operations that you can perform forvolumes based on the access attributes that you set.

The following table shows the SS pool operations that you can perform forvolumes based on the access attributes that you set.

Note: Use the CCI to set the Zero Read Capacity and Invisible attributes.

Note: The SS volume access attributes do not change as a result of anSS operation. For example, even though the reverse resync operationreverses the P-VOL and S-VOL, the P-VOL access attribute is notoverwritten to that S-VOL.

SS pair P-VOLaccess attribute

SS pair S-VOLaccess attribute

SS pair operation

Create, Split, Suspend,Delete, Resync (forward)

Resync (reverse)

Read/Write Read/Write YES YES

Read Only, Protect,S-VOL Disable

NO NO

Read Only Read/Write YES NO


NO NO

Protect Read/Write YES NO


NO NO

S-VOL Disable Read/Write YES NO

Read Only, Protect,

S-VOL Disable

NO NO

SS volume accessattribute

SS pool operation

Pool-VOL setting

Read/Write YES

Read Only NO

Protect NO

S-VOL Disable NO


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The SS pair status determines whether you can set access attributes for theSS P-VOL and S-VOL. The following table shows the access attributes thatyou can set for SS P-VOL and S-VOL.

Dynamic Provisioning

You can share HDP volumes with SS P-VOLs. You can use a maximum HDPvolume size of 4 TB (4398046511104 bytes) as an SS P-VOL.

You cannot use TB, GB, or MB specifications for SS volumes. For example,to create a 4 TB P-VOL, use the block specification. The block-sizeequivalent to 4 TB is 8589934592 blocks.

Note the following regarding pools:

• You cannot use HDP pools (including Dynamic Tiering (HDT) pools) asSS pools.

• The number of available pools for SS decreases according to the numberof HDP pools (including HDT pools) and HDPz pools in the storagesystem. You can create a maximum of 128 pools in the storage system.

• If you specify an HDP V-VOL as the SS P-VOL and the capacity of theHDP V-VOL is increasing, you cannot create the SS pair.

• Performing an SS paircreate operation while zero pages are beingreclaimed (including operations by Writesame, Unmap, and Rebalance)results in the zero-page operation being interrupted.

• An SS create pair operation may be rejected if the Unmap commandoperation is in progress with system option mode 905 ON. Retry the SSoperation after a while. If the operation still fails, set system optionmode 905 to OFF and retry.

SS pair status SS pair volume

Access attribute setting


Read/Write

COPY P-VOL YES YESS-VOL NO YES

PAIR, PFUL P-VOL YES YES

S-VOL YES YES

PSUS, PFUS P-VOL YES YES

S-VOL YES YES

SMPL P-VOL YES YES

S-VOL NO YES

RCPY P-VOL NO YES

S-VOL NO YES

PSUE P-VOL YES YES

S-VOL NO YES


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Resource Partition Manager

You can create an SS pair if the P-VOL and S-VOL are allocated to the sameresource group or different resource groups. Allocate the pool you want touse to the same resource group as the P-VOL or the resource group that hasan authority to create an SS pair.

For more information about resource groups, see the Hitachi Virtual StoragePlatform Provisioning Guide for Open Systems.

ShadowImage

You can share SI P-VOLs and S-VOLs with SS P-VOLs. The SI and SS pair’sstatus determines the pair operations you can perform.

For more information about SI pair status and operations, see the HitachiShadowImage® User Guide.

The following tables list the relationship between SS pair operations and SIstatus.

The following tables list the relationship between SS operations and SIstatus.

SS pairoperation

SI status

COPY (PD) /COPY

PAIR COPY (SP) /COPY

PSUS(SP) /PSUS

PSUSCOPY(RS) /COPY

COPY(RS-R) /

RCPY PSUE

Create pair Yes Yes Yes Yes Yes Yes No Yes

Split pair Yes Yes Yes Yes Yes Yes No Yes

Restore pair No No No No Yes No No Yes

Delete SS data Yes Yes Yes Yes Yes Yes Yes Yes

Delete pair Yes Yes Yes Yes Yes Yes Yes Yes

SS operation

SI status

COPY (PD)

/COPY

PAIR COPY(SP) /COPY

PSUS(SP) /PSUS

PSUSCOPY(RS) /COPY

COPY(RS-R) /

RCPY PSUE

Create pair No No No No Yes No No No

Split pair N/A No No No Yes No No No

Split pair in a

consistencygroup

N/A No No No Yes* No No No

Restore pair N/A No No No Yes No No No

Delete SS data N/A Yes Yes Yes Yes Yes Yes Yes

Delete pair N/A Yes Yes Yes Yes Yes Yes Yes


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The following tables list the relationship between SI operations and SSstatus.

The following tables list the relationship between SI operations and SSstatus.

* The SI pair status must be “PSUS” from the time you split the pairs in a consistencygroup until the time the status of all SS pairs in the consistency group change to

“PSUS”. If the SI pair status changes while splitting pairs in a consistency group, theSS data cannot maintain consistency.

SS operation

SI status

COPY (PD)

/COPY

PAIR COPY(SP) /COPY

PSUS(SP) /PSUS

PSUSCOPY(RS) /COPY

COPY(RS-R) /

RCPY PSUE

SI operation

SS status

COPY 1PAIR,PFUL

PSUS,PFUS

COPY 2 RCPY PSUE

Create pair Yes Yes Yes Yes No Yes

Create and split pair Yes Yes Yes Yes No Yes

Split pair Yes Yes Yes Yes No Yes

Forward pairresynchronization

Yes Yes Yes Yes No Yes

Normal backward pairresynchronization


Quick backward pairresynchronization

No No No No No No

Suspend pair Yes Yes Yes Yes Yes Yes

Delete pair Yes Yes Yes Yes Yes Yes

1. “COPY” status during initial copy.

2. “COPY” status during resynchronization.

SI operation

SS status

COPY 2PAIR,PFUL

PSUS,PFUS

COPY 3 RCPY PSUE

Create pair No No No No No No

Create and split pair No No No No No No

Split pair Yes Yes Yes Yes No Yes

Forward pairresynchronization


Normal backward pairresynchronization


Quick backward pairresynchronization

No No No No No No

Suspend pair Yes Yes Yes Yes No Yes


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Restrictions when sharing P-VOLs

The SS S-VOL uses the data in the P-VOL. The following are restrictionswhen sharing an SS pair P-VOL with an SI P-VOL or S-VOL:

• The SS pair P-VOL cannot have the same mirror unit (MU) number asthe SI pair.

• You cannot perform the SI Quick Restore operation.

• You cannot share the SI volume that is in a consistency group with SS.

• You cannot share the SS volume that is in a consistency group with SI.

TrueCopy and Universal Replicator

You can share TC and UR pair volumes with SS P-VOLs. If you share pairvolumes with these software applications, the pair operation you canperform are restricted based on the shared pair status.

The following table shows the relationship between SS pair operations andTC/UR status.

The following table shows the relationship between SS pair operations andTC/UR status.

Delete pair Yes Yes Yes Yes Yes Yes

1. You can perform SI operations while splitting pairs in a consistency group. However,the SS data consistency is not maintained.

2. “COPY” status during initial copy.

3. “COPY” status during resynchronization.

SI operation

SS status

COPY 2PAIR,PFUL

PSUS,PFUS

COPY 3 RCPY PSUE

SS operation

TC/UR status

COPY PAIR PSUS PSUE Suspen

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