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Hitachi Simple Modular Storage Copy-on-
Write SnapShot User’s Guide
FASTFIND LINKS
Document Organization
Product Version
Getting Help
Table of Contents
MK-97DF8018-00
# i
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© 2007 Hitachi Data Systems Corporation, ALL RIGHTS RESERVED Notice: No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or stored in a database or retrieval system for any purpose without the express written permission of Hitachi Data Systems Corporation (hereinafter referred to as “Hitachi Data Systems”). Hitachi Data Systems reserves the right to make changes to this document at any
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Preface This document provides instructions on assessing your snapshot requirements, designing an implementation to meet those requirements, and implementing and operating Copy-on-Write Snapshot software using the Storage Navigator 2 graphical user interface. This preface includes the following information: • Document Revision Level • Safety and Warnings • Product Version • Release Notes • Referenced Documents • Document Conventions • Convention for Storage Capacity Values • Getting Help • C
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Document Revision Level This section provides a history of the revision changes to this document. • Revision Date Description MK-97DF8018-00 October 2007 Initial Release Safety and Warnings This document uses the following symbols to draw attention to important safety and operational information. The Danger, Electric Shock, and ESD symbols are included only in hardware manuals. • Symbol Meaning Description Tip Tips provide helpful information, guidelines, or suggestions for performing tasks m
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Document Organization The following table provides an overview of the contents and organization of this document. Click the chapter title in the first column to go to that chapter. The first page of every chapter or appendix contains a brief list of the contents of that section of the manual, with links to the pages where the information is located. • Chapter/Appendix Description Title Provides descriptions of SnapShot components and how Chapter 1, SnapShot they work together. Overview Pro
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Document Conventions The following table describes the typographic conventions used in this document. • Convention Description Bold Indicates text on a window, other than the window title, including menus, menu options, buttons, fields, 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 indicate variables. screen/code Indicates t
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Getting Help If you have questions after reading this guide, contact an Hitachi Data Systems authorized service provider[H1] or visit the Hitachi Data Systems support website, http://support.hds.com. Support Contact Information If you purchased this product from an authorized Hitachi Data Systems reseller, contact that reseller for support. For the name of your nearest Hitachi Data Systems authorized reseller, refer to the Hitachi Data Systems support web site for locations and contact info
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viii Preface Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
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Table of Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Document Revision Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Safety and Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Intended Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Product Version. . . . . . . . . . . . . .
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Lifespan Based on Backup Requirements . . . . . . . . . . . . . . . . . . . . . . . 2-3 Lifespan Based on Business Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 Establishing the Number of V-VOLs that Are Required. . . . . . . . . . . . . . . . 2-4 Establishing Data Pool Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 Measuring Workload Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 Rule of Thumb Calculation .
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7 Monitoring and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 Monitoring SnapShot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Monitoring Pair Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Monitoring Data Pool Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 Expanding the Data Pool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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xii Contents Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
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1 SnapShot Overview Snapshot creates virtual copies of data volumes within Hitachi Simple Modular Storage systems. These copies can be used for recovery from logical errors. They are identical to the original volume at the point in time they were taken. This guide provides instructions for planning and designing, configuring and testing, and using and monitoring SnapShot. In this chapter, see: Copy-on-Write SnapShot Software Hardware and Software Configuration How SnapShot Works SnapSho
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Copy-on-Write SnapShot Software Hitachi’s Copy-on-Write Snapshot software creates virtual backup copies of any data volume within the Simple Modular Storage systems with minimal impact to host service or performance levels. These snapshots are suitable for immediate use in decision support, software testing and development, data backup, or rapid recovery operations. SnapShot minimizes disruption of planned or unplanned outages for any application that cannot tolerate downtime for any reaso
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• Figure 1-1: SnapShot functional components The following sections describe how these components work together. How SnapShot Works SnapShot creates a virtual duplicate volume of another volume. This volume “pair” is created when you: • Select a volume that you want to replicate • Identify another volume that will contain the copy • Associate the primary and secondary volumes • Create a snapshot of the primary volume data in the virtual (secondary) volume. Until the new or re-synchronized p
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Volume Pairs—P-VOLs and V-VOLs A volume pair is a relationship established by SnapShot between two volumes. A pair consists of a production volume, which contains the original data and is called the primary volume (P-VOL), and from 1 to 32 virtual volumes (V-VOLs), which contain copies of the P-VOL. The P-VOL and its V- VOL(s) are located in the same Simple Modular Storage system. A V-VOL is a mirror image of the P-VOL at the time of the snapshot. Unlike the P-VOL, which contains the actua
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• Figure 1-2: V-VOL Maintains SnapShot Data SnapShot Overview 1–5 Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
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Data Pools After a snapshot, the V-VOL maintains a static copy of the P-VOL even as new writes are updating the P-VOL. To do this, before an updated block is written to the P-VOL, SnapShot sends the data that is being replaced to the data pool. Pointers in the V-VOL are updated to locate the replaced data that is now located in the data pool, thus maintaining the V-VOL point-in-time image of the P-VOL. The data pool’s function in the SnapShot process is illustrated in Figure 1-2. Up to 64
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222 Planning and Design A backup insures that a volume with bad or missing data can be restored. With SnapShot you create copies of your production data that can be used for backup and other uses. Creating a backup system that fully supports business continuity is best done when SnapShot is configured to match your business needs. This chapter guides you in planning a configuration that meets organization needs and the workload requirements of your host application. The Plan and Design
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The Plan and Design Workflow The SnapShot planning effort consists of finding the number of V-VOLs your organization requires for the P-VOL, the V-VOL(s)’ lifespan — how long they must be held before being updated again — the frequency that snapshots are taken, and the size of the data pool. The answers are determined by analyzing the organization’s business needs and measuring the write workload that is generated by the host application. The plan and design workflow consists of the follo
