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EMC Corporation171 South StreetHopkinton, MA 01748-9103Corporate Headquarters: (508) 435-1000, (800) 424-EMC2Fax: (508) 435-5374 Service: (800) SVC-4EMC

EMC SnapViewVersion 1.X

ADMINISTRATOR’S GUIDEFor Navisphere 5.X

P/N 069001155REV A01

EMC SnapView Administrator’s Guide for Navisphere 5.Xii

Copyright © 2002 EMC Corporation. All rights reserved.Printed March, 2002

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.

Trademark InformationEMC2, EMC,CLARiiON, and Navisphere are registered trademarks and Access Logix, MirrorView, and SnapView are trademarks of EMC Corporation.All other trademarks used herein are the property of their respective owners.

EMC SnapView Administrator’s Guide for Navisphere 5.X iii

Preface.............................................................................................................................. v

Chapter 1 About EMC SnapView SoftwareWhat Is SnapView? .......................................................................... 1-2How SnapView Works .................................................................... 1-5

Chapter 2 Setting Up and Using SnapView Version 1.3x (or Higher)SnapView Requirements................................................................. 2-2

Setting Up SnapView Version 1.3x (or Higher) ................... 2-2Configuration Guidelines ............................................................... 2-3SnapView Operations Overview ................................................... 2-4

Snapshot Session Overview .................................................... 2-7Using SnapView............................................................................... 2-8Snapshot Cache ................................................................................ 2-8

Binding LUNs for the Snapshot Cache.................................. 2-9Snapshot Cache Size................................................................. 2-9Configuring an SP’s Snapshot Cache................................... 2-10

Creating a Snapshot....................................................................... 2-13Adding a Snapshot to a Storage Group............................... 2-15Creating Multiple Snapshots ................................................ 2-16Activating a Snapshot ............................................................ 2-16Deactivating a Snapshot ........................................................ 2-18Destroying a Snapshot ........................................................... 2-19

Starting a Snapshot Session .......................................................... 2-20Normal Mode Snapshot Session........................................... 2-20Simulation Mode Snapshot Session ..................................... 2-22Multiple Snapshot Sessions................................................... 2-23Stopping a Snapshot Session................................................. 2-24

Contents

EMC SnapView Administrator’s Guide for Navisphere 5.Xiv

Contents

Chapter 3 Setting Up and Using SnapView Version 1.2x (or Lower)SnapView Requirements................................................................. 3-2

Setting Up SnapView Version 1.2x (or Lower) .................... 3-2SnapView Operations Overview................................................... 3-3

Snapshot Session Overview .................................................... 3-6Using SnapView............................................................................... 3-7Snapshot Cache ................................................................................ 3-7

Binding LUNs for the Snapshot Cache ................................. 3-7Snapshot Cache Size................................................................. 3-8Configuring an SP’s Snapshot Cache .................................... 3-8

Creating a Snapshot....................................................................... 3-11Adding a Snapshot to a Storage Group .............................. 3-13Destroying a Snapshot........................................................... 3-14

Starting a Snapshot Session.......................................................... 3-15Normal Mode Snapshot Session .......................................... 3-15Simulation Mode Snapshot Session..................................... 3-17Stopping a Snapshot Session ................................................ 3-18

Chapter 4 Displaying SnapView PropertiesDisplaying SnapView Properties................................................... 4-2Displaying Status of All Snapshots and Snapshot Sessions ...... 4-5

Glossary ........................................................................................................................ g-1

Index................................................................................................................................ i-1

EMC SnapView Administrator’s Guide for Navisphere 5.X v

Preface

This guide is part of the SnapView™ documentation set, and is intended for use by customers and service providers using Navisphere® Manager to set up and manage SnapView.

Readers of this guide are expected to be familiar with EMC Navisphere Manager.

Organization Here is an overview of where information is located in this guide.

Chapter 1 Introduces the EMC SnapView software application, which creates a snapshot of a LUN that can be used for decision support, testing, or backup while the production work continues.

Chapter 2 Describes how to set up and use SnapView version 1.3x (or higher). This chapter also lists the requirements and configuration guidelines for SnapView version 1.3x.

Chapter 3 Describes how to set up and use SnapView version 1.2x (or lower). This chapter also lists the requirements and configuration guidelines for SnapView version 1.2x.

Chapter 4 Describes how to display the Properties dialog box for each SnapView component.

vi EMC SnapView Administrator’s Guide for Navisphere 5.X

Preface

Conventions Used inThis Guide

EMC uses the following conventions for notes, cautions, warnings, and danger notices.

A note presents information that is important, but not hazard-related.

CAUTION!A caution contains information essential to avoid data loss or damage to the system or equipment. The caution may apply to hardware or software.

WARNING

A warning contains information essential to avoid a hazard that can cause severe personal injury, death, or substantial property damage if you ignore the warning.

DANGER

A danger notice contains information essential to avoid a hazard that will cause severe personal injury, death, or substantial property damage if you ignore the message.

Typographical ConventionsEMC uses the following type style conventions in this guide:

AVANT GARDE Keystrokes

Palatino,bold

◆ Dialog box, button, icon, and menu items in text◆ Selections you can make from the user interface,

including buttons, icons, options, and field names

Palatino,italic

◆ New terms or unique word usage in text ◆ Command line arguments when used in text◆ Book titles

EMC SnapView Administrator’s Guide for Navisphere 5.X vii

Preface

Where to Get Help For questions about technical support and service, contact your service provider.

If you have a valid EMC service contract, contact EMC Customer Service at:

Follow the voice menu prompts to open a service call, then select CLARiiON Product Support.

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For the list of EMC sales locations, please access the EMC home page at:

http://www.emc.com/contact/

For additional information on the EMC products and services available to customers and partners, refer to the EMC Powerlink Web site at:

http://powerlink.emc.com

Your Comments Your suggestions will help us continue to improve the accuracy, organization, and overall quality of the user publications. Please send a message to [email protected] with your opinions of this guide.

Courier, italic

Arguments used in examples of command line syntax.

Courier System prompts and displays and specific filenames or complete paths. For example:

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Courier, bold

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viii EMC SnapView Administrator’s Guide for Navisphere 5.X

Preface

About EMC SnapView Software 1-1

1Invisible Body Tag

This chapter introduces SnapView™ software.

All references to an FC4700 storage system are to both the FC4700 and the FC4700-2 storage system.

Major sections are

◆ What Is SnapView? ............................................................................1-2◆ How SnapView Works ......................................................................1-5

About EMC SnapViewSoftware

1

1-2 EMC SnapView Administrator’s Guide for Navisphere 5.X

About EMC SnapView Software

What Is SnapView?SnapView is a software application that creates a snapshot image of a LUN and retains the image independently of subsequent changes to the LUN. The snapshot image can serve as a base for decision support, revision testing, backup, or in any situation where you need a consistent, copyable image or real data. SnapView can create or destroy a snapshot in seconds, regardless of the LUN size, since it does not actually copy data.

SnapView Benefits SnapView provides the following important benefits:

◆ It allows full access to production data with modest impact on performance.

◆ For decision support or revision testing, it provides a coherent, readable and writable copy of real production data at a particular point in time.

◆ For backup, it practically eliminates the time that production data spends off line or in hot backup mode. And it offloads the backup overhead from the production host to another host.

SnapView SoftwareComponents

SnapView consists of the following software components:

◆ A driver that provides the SnapView functionality, and resides on the storage system with LUNs you want to copy.

◆ The admsnap utility that provides a command line executable that lets you manage SnapView sessions, and resides on the hosts connected to the storage system that has the SnapView driver.

EMC provides two different ways for you to set up and manage the functionality provided by the SnapView driver:

◆ Graphical User Interface (GUI) - Navisphere® Manager, which is a separately ordered product.

◆ Command Line Interface (CLI) - Navisphere CLI, which ships as part of the Navisphere Host Agent packages.

You use Manager or CLI, not admsnap, to set up SnapView; and then you can use either Manager, CLI, or admsnap to manage SnapView sessions.

1

What Is SnapView? 1-3


SnapView Hosts SnapView requires at least two hosts, one host (called the production host) that contains the LUN you want to copy and another host (called the second host) that lets you view the snapshot data. You can have multiple second hosts.

The production host is the system that

◆ runs the customer applications.◆ owns the source LUN.

The second host (or any other host) is the system that

◆ owns the snapshot.◆ reads from or writes to the snapshot during the snapshot session.◆ performs an independent analysis or backup task using the copy.

Figure 1-1 shows a sample SnapView environment with snapshot sessions of a database and its log.

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Figure 1-1 Sample SnapView Environment with Snapshot Sessions of a Database and Its Log

EMC2283

LAN

Windows Host

NavisphereManagement Station

Connection forManager only

Snapview Driver

SnapViewSource LUN 1

(Database Log)

SnapViewSource LUN 2

(Database Files)

LUN 3

LUN 4

SnapViewSnapshot of LUN 1

(Database Log)

SnapViewSnapshot of LUN 2

(Database Files)

LUN 13

FC4700

Production Host

Optional CLIadmsnap

Second Host

Optional CLIadmsnap

Production Host’sStorage Group

Second Host’sStorage Group

NavisphereManager GUI

1

How SnapView Works 1-5


How SnapView WorksThe snapshot session begins when the SnapView driver receives and processes a start command and ends when the driver receives and processes a stop command.

The snapshot allows you to view point-in-time data of the source LUN (the LUN being snapped). When the original data on the source LUN is modified, a copy of that data is stored in the snapshot cache in chunk sizes. This copy happens only once, when the data is first modified.

The snapshot views the original data chunks from the snapshot cache instead of the source LUN because the original data is no longer located on the source LUN. As time passes, and I/O modifies the source LUN, the amount of data chunks stored in the snapshot cache grows. However, the snapshot will continue to view any unchanged data from the source LUN.

The snapshot does not reside on a disk like a conventional LUN, and it does not occupy any disk space. However, the snapshot appears as a conventional LUN to another host. SnapView can also create or destroy a snapshot in seconds, regardless of the LUN size, since it does not actually copy data.

The following figure shows an overview of how SnapView works.

Figure 1-2 SnapView Overview

EMC1822

ContinuousI/O

The snapshot is a composite of the source LUN and the snapshot cache.

Storage system

Snapshot

Snapshot

cacheSourceLUN

Productionhost

Secondhost

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Setting Up and Using SnapView Version 1.3x (or Higher) 2-1

2Invisible Body Tag

This chapter describes how to set up and use SnapView version 1.3x (or higher).

Determining your SnapView version - From the Enterprise Storage dialog box click the Storage tab; right-click the storage system icon; click Properties; click the Software tab; and, in the Packages list view the version of SnapView.

The following features are available with this version of SnapView:

◆ Multiple snapshots per source LUN

◆ Multiple snapshot sessions per source LUN

Major sections in this chapter are

◆ SnapView Requirements ...................................................................2-2◆ Configuration Guidelines .................................................................2-3◆ SnapView Operations Overview .....................................................2-4◆ Using SnapView .................................................................................2-8◆ Snapshot Cache ..................................................................................2-8◆ Creating a Snapshot.........................................................................2-13◆ Starting a Snapshot Session ............................................................2-20

Setting Up and UsingSnapView

Version 1.3x (or Higher)

2


Setting Up and Using SnapView Version 1.3x (or Higher)Setting Up and Using SnapView Version 1.3x (or Higher)

SnapView RequirementsTo ensure that you have the most up-to-date information about the SnapView driver, EMC posts the release notes for this driver on the EMC Powerlink web site. We recommend that you download a copy of the release notes before you start the Manager software. To access EMC powerlink use the following url:


After you log in, select Services → Document Library → CLARiiON → CLARiiON Fibre Channel Storage → CLARiiON FC Software, and find the EMC SnapView and Admsnap Release Notes (P/N 085090552).

SnapView has the following requirements:

◆ Any FC4700 storage system that you want to manage, must have SnapView installed.

◆ Access Logix™ must be installed on the same FC4700 storage system that is running SnapView.

◆ The snapshot cache must be established on one or more LUNs that do not belong to any Storage Groups.

◆ Before or after starting a snapshot session, the snapshot you map to a session must belong to a Storage Group and the Storage Group must connect to a host.

◆ The source LUN and snapshot must be assigned to different Storage Groups. The source LUN Storage Group should be accessible to the production host and the snapshot Storage Group to the other host.

Setting Up SnapView Version 1.3x (or Higher)

Before starting a snapshot session, you must complete the following tasks.

◆ Make sure that you have bound LUNs available for the snapshot cache. See Binding LUNs for the Snapshot Cache on page 2-9.

◆ Configure the snapshot cache. See Configuring an SP’s Snapshot Cache on page 2-10.


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Configuration Guidelines 2-3

Setting Up and Using SnapView Version 1.3x (or Higher)

Configuration GuidelinesThe following table lists the configuration guidelines for SnapView.

A clustered server can be configured to access a source LUN, but not both the source LUN and its snapshot. The snapshot must be accessed only by a host outside the cluster.

Table 2-1 SnapView Configuration Guidelines

Parameter Maximum Number

Snapshot Cache LUNs

Per Storage System 100 maximum

Snapshots

Per Source LUN 8 maximum

Per Storage System 300 maximum

Snapshot Sessions

Per Source LUN 8 maximum

Per Storage System 100 maximum concurrent sessions (sessions running at the same time)

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SnapView Operations Overview The section is an overview of the operations you need to perform when using SnapView version 1.3x (or higher).

1. On an SP determine how many source LUNs you want a snapshot of. The size of these LUNs will help you decide on an approximate snapshot cache size.

The LUN(s) in the snapshot cache are needed to store the original data when that data is first modified on the source LUN. The snapshot cache can use any public LUN that is not part of any Storage Group. (This requires forethought, since normally you assign each LUN that will store user data to a Storage Group.)

The snapshot cache pool should be large enough for all concurrent sessions on that SP. This is why an adequate snapshot cache size is essential. If you run out of cache space while a snapshot session is running, your session will be terminated.

A general guideline for snapshot cache size is 10% of the size of the LUN you want to copy; however, you may want to use a larger cache size, such as 20%, 50%, or even 100%, depending on how many snapshot sessions you will be running per source LUN. See Snapshot Cache Size on page 2-9.

SnapView also has a simulation mode option to help you determine an ideal snapshot cache size. See Simulation Mode Snapshot Session on page 2-22.

2. On the storage system, bind one or more LUNs on an SP to the size you determined for the snapshot cache.

3. On the storage system that owns the source LUN, allocate the snapshot cache.

You allocate LUNs to the snapshot cache using the Manager Snapshot Cache Properties dialog box.

A snapshot cache LUN(s) is shared by all snapshot sessions running on a specific source LUN. If the snapshot cache size is too small, you can add additional LUNs to the snapshot cache pool or terminate a session to free its cache space. However, if you are running multiple snapshot sessions per source LUN, all sessions on that source LUN must be stopped in order to free cache space.

2

SnapView Operations Overview 2-5


If the snapshot cache fills up, SnapView terminates the session that encountered the error, logs an error, and releases the snapshot cache space used by that session or sessions.

When you allocate the snapshot cache, you specify a cache chunk size. The chunk size is the size of each snapshot cache write. With the default chunk size of 128 Kbytes, the software divides the source LUN into 128-Kbyte blocks and, if any part of a 128-Kbyte block is changed during the session, the software retains the original image of that block in the snapshot cache. The chunk size applies to both SPs. You can change the chunk size after you allocate the cache if there are no snapshot sessions running on the storage system.

4. Create a snapshot and start a snapshot session.

With SnapView version 1.3x (or higher) it does not matter whether you create a snapshot first or start a snapshot session first. See Creating a Snapshot on page 2-13 andStarting a Snapshot Session on page 2-20.

• On the storage system that owns the source LUN, create a snapshot using Navisphere Manager or CLI.

You must assign the snapshot to a Storage Group other than the Storage Group that holds the source LUN. Make sure that the snapshot Storage Group is accessible by the second or any other host. Navisphere Manager will prompt you for this. This step is needed only once.

• On the storage system that owns the source LUN, start a snapshot session.

You can start a snapshot session using the Navisphere Manager Start Snapshot Session function or the admsnap start operation. The session name identifies the session. You create the name when you start a snapshot session, use it to activate the snapshot and then use it to stop the session.

5. On the second host, identify the snapshot to the operating system. This procedure depends on the operating system; for example, with Microsoft Windows® systems you need to run Disk Admin. This step is needed only once, as part of the SnapView initial setup.

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6. On the second host, do the following to make the new session available:

Use the admsnap activate command as explained in the Admsnap Host Management Utility Administrator’s Guide. On a Windows system, the admsnap command returns a drive letter that you can use immediately to access the snapshot data. On a UNIX® system, the command returns a device name on which you must run fsck and then mount to make a file system available for use.

If you have not installed admsnap, use the Navisphere Manager activate function to map the snapshot to the session, then you must reboot the second host or, using some other means, cause it to recognize the new device created when you started the snapshot session. Installing admsnap is explained in the Admsnap Host Management Utility Administrator’s Guide.

7. On the second host, use the snapshot data as desired for modeling, testing, or backup. As needed, mount any file systems or start database software to analyze the snapshot data or back it up.

8. Before stopping the snapshot session, make the snapshot session unavailable to the second host by doing one of the following:

• Use the admsnap deactivate command as explained in the Admsnap Host Management Utility Administrator’s Guide. On a UNIX system, use the umount command.

• Use the Navisphere Manager deactivate command to deactivate the snapshot remotely.

The Navisphere Manager deactivate function does not flush all data and clear all buffers on the second host. To flush I/O from this host use the admsnap deactivate utility command on this host.

9. On the storage system that owns the source LUN, stop the snapshot session.

You can stop the session using Manager, CLI or admsnap. Stopping a session frees the snapshot cache space and any SP memory used for the session. The newly freed snapshot cache space becomes available for other snapshot sessions. However, if you are running multiple snapshot sessions per source LUN, all sessions on that source LUN must be stopped in order to free cache space.

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Snapshot Session Overview

The following figure shows how a snapshot session starts, runs, and stops.

In the following figure, the production host and source LUN are in one Storage Group. The second host and snapshot are in another Storage Group.

Figure 2-1 How a Snapshot Session Starts, Runs, and StopsEMC2229

ProductionHost

SecondHost

SourceLUN

SnapshotSnapshotcache

1. Before session starts

SourceLUN

SnapshotCache

ProductionHost

SecondHost

2. Start session (2:00 p.m.)

SourceLUN

SnapshotCache

ProductionHost

SecondHost

7. Stop session (4:25 p.m.)

5. End operation (4:15 p.m.)

ProductionHost

SecondHost

SourceLUN

Snapshot(pointers tochunks)

Cache

6. Deactivate snapshot (4:16 p.m.)

ProductionHost

SecondHost

SourceLUN


Cache

3. Activate snapshot (2:01 p.m.)

Productionhost

Secondhost

SourceLUN


Cache

4. Begin operation, suchas back-up or decisionsupport (2:02 p.m.)

Productionhost

Secondhost

SourceLUN


Cache

Changed chunkson source LUN

Unchanged chunks incache and snapshot

Unchanged chunkson source LUN

Key:

2



Using SnapViewWith Navisphere Manager you can use SnapView to:

◆ Create snapshots (see Creating a Snapshot on page 2-13)

◆ Start and stop snapshot sessions (see Starting a Snapshot Session on page 2-20 and Stopping a Snapshot Session on page 2-24)

◆ Display the status and properties of the snapshot cache, snapshot sessions, and snapshots (see Chapter 4, Displaying SnapView Properties)

If the MirrorView option is installed, we recommend that you do not take a snapshot of the remote mirror secondary copy while the secondary copy is being synchronized. The data may not be useful.

With SnapView version 1.3x (or higher), you do not need to create a snapshot in order to start a snapshot session. However, you must create a snapshot in order for a session to be viewed by another host. Refer to Activating a Snapshot on page 2-16.

Snapshot CacheFor SnapView version 1.3x (or higher), snapshot cache LUNs are dedicated on a per source LUN basis. The SP manages the snapshot cache space and apportions it to all snapshot sessions running on that specific source LUN. For example, if two snapshot sessions are running on a source LUN (see Multiple Snapshot Sessions on page 2-23), both of these snapshot sessions will allocate cache space from the same snapshot cache LUN. Once the cache LUN is filled, an additional cache LUN is assigned to the current snapshot sessions. The assignment of cache LUNs is based upon the first available LUN in the snapshot cache.

If you intend to create snapshots for LUNs owned by SP A and LUNs owned by SP B, configure the snapshot cache for each SP, as described in Configuring an SP’s Snapshot Cache on page 2-10.

You must have at least one snapshot cache LUN for each source LUN for which you want to start a snapshot session.

2

Snapshot Cache 2-9


Binding LUNs for the Snapshot CacheBefore binding LUNs for the snapshot cache, think about which source LUNs will participate in a snapshot session. The size of these LUNs will help you determine an approximate snapshot cache size. To bind LUNs refer to the section Creating LUNs on RAID Groups, in EMC’s Navisphere Manager Version 5.X Administrator’s Guide.

The snapshot cache must be established on one or more LUNS that do not belong to any Storage Group.

Snapshot Cache Size

An adequate number of snapshot cache LUNs is essential because sessions can be terminated if the snapshot cache runs out of space. If you are running multiple sessions per source LUN and your snapshot cache LUN fills up (runs out of space) and there are no additional cache LUNs available in the snapshot cache, the session that is trying to allocate cache space from this cache will be terminated. The other sessions running on this source LUN will continue to run and use the cache space that was freed by the session that was terminated. If you are running only one session per source LUN and no additional cache LUNs are available in the SP’s cache pool, the session that is trying to allocate cache space will be terminated. The cache LUNs used by this session will be freed and returned to the cache pool.

Each snapshot cache LUN can vary in size. However, using the same cache size for each LUN is easier to manage because cache LUNs are assigned without regard to size. The assignment of cache LUNs is simply based upon the first available LUN in the snapshot cache. Since you cannot control which cache LUNs are being used for a particular snapshot session, it is recommended that you use smaller and more cache LUNs. By using smaller cache LUNs, cache space will not go unused. If more cache space is required, another cache LUN will be dynamically assigned.

You can manually estimate a suitable snapshot cache size or you can run a snapshot session in simulation mode (see page 2-22) to help you determine the size. To manually estimate a suitable snapshot cache size, add the total size of source LUNs in SP A or SP B, multiply that number by 10% (this is the cache usage) and then multiply that amount by two (this is a buffer for any unanticipated I/O to the source LUN). The result is the size you want your snapshot cache to

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be. To determine the size of each cache LUN, divide the snapshot cache size by two times the number of snapshots. The result is the size of each cache LUN. The number of cache LUNs should always be two times the number of snapshots.

If several snapshot sessions are running on an SP or multiple snapshot sessions are running on a LUN, and you determine that the snapshot cache size is running out of space, you can terminate a session to free its cache space, or you can add LUNs to the snapshot cache while the session is active. If the snapshot cache fills up, the software automatically terminates the session that encountered the error, logs an error, and releases the snapshot cache space used by that session. At this point, the snapshot becomes inactive and any host that has mounted volumes on the snapshot will receive I/O errors and lose access.

If you intend to write to the snapshot, make sure that the snapshot cache is large enough to store these writes, since all writes to the snapshot are stored in the snapshot cache.

Stopping a session (or having one terminated) frees the associated cache space, so if you are near the limit and there is one snapshot session that is less important to you than another, you can terminate the less important session to free cache space for the more important ones.

If you are running multiple snapshot sessions per source LUN, all sessions on that source LUN must be stopped in order to free cache space for use by sessions on a different source LUN.

Configuring an SP’s Snapshot CacheThe snapshot cache consists of one or more private LUNs, and the size of the snapshot cache is the aggregate of all these LUNs. The LUNs in the snapshot cache are needed to store blocks of the original data when that data is first updated on the source LUN. For any one snapshot session, the contents of the snapshot cache and any unchanged source LUN blocks comprise the snapshot. The SP that owns the snapshot source LUN must own the snapshot cache LUNs. The SP manages the snapshot cache space and apportions a separate snapshot cache LUN (or multiple LUNs) to each snapshot session.

2

Snapshot Cache 2-11


Each SP has its own snapshot cache, and before starting a snapshot session, the snapshot cache must contain at least one LUN. You can increase or decrease the size of the snapshot cache by adding or removing LUNs.

To Configure an SP’sSnapshot Cache

If you plan to create snapshots for LUNs owned by SP A and LUNs owned by SP B, configure the snapshot cache for each SP.

1. In the Enterprise Storage dialog box, click the Storage tab.

2. Double-click the icon for the storage system for which you want to configure the snapshot cache, and double-click Snapshot Cache.

3. Right-click either the SP A or SP B cache icon, and click Properties.

The Snapshot Cache Properties dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

4. In Chunk Size (Blocks), select the chunk size (size of each snapshot cache write) for both SPs.

5. In Available LUNs, select the LUNs that you want to add to the snapshot cache for each SP.

Available LUNs lists only those LUNs that are eligible for inclusion in the snapshot cache.

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If there are no LUNs in the list or if none of the available LUNs are the necessary size, you must bind new LUNs and then add them to the snapshot cache. To bind LUNs, refer to the section Creating LUNs on RAID Groups, in EMC’s Navisphere Manager Version 5.X Administrator’s Guide.

6. To add the selected LUNs to SP A’s snapshot cache, click Add to SP A Cache; to add the LUNs to SP B’s cache, click Add to SP B Cache.

The selected LUNs move to the SP Cache Member LUNs list for SP A or SP B, and the value in Modified Capacity is updated to reflect the changes.

Modified Capacity is the current size of the SP’s snapshot cache.

7. To remove LUNs from the SP Cache Member LUNs list, select the LUNs you want to remove, and then click Remove from Cache.

Only unallocated (free) cache LUNs can be removed from the SP Cache Member LUNs list.

8. When you have added all the LUNs you want to the snapshot cache, click OK to apply the changes and close the dialog box.

The snapshot cache LUNs are added to either the SP A Cache or SP B Cache container in the Storage tree.

2

Creating a Snapshot 2-13


Creating a SnapshotAn active snapshot is a composite of the source LUN and snapshot cache data that lasts until it is destroyed. Each snapshot is linked to a source LUN. If the storage system loses power while the session is running, the session is lost and the snapshot becomes inactive.

To Create a Snapshot 1. In the Enterprise Storage dialog box, click the Storage tab.

2. Double-click the icon for the storage system on which the source LUN resides.

3. Double-click the icon for the SP to which the source LUN belongs.

4. Right-click the icon for the source LUN, and then click Create Snapshot.

The Create Snapshot dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

5. In Storage System and Snapshot Source LUN, verify that you are creating the snapshot for the correct source LUN on the correct storage system.

6. In Snapshot Name, enter a unique name for the snapshot. If the Snapshot Name is left blank, the default name SCLUN 0xn is assigned to the snapshot, where n is an incremented internal number that is assigned to the snapshot.

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If you enter an invalid name and then click OK, the application displays an error message.

7. In Storage Group, select the Storage Group to which you want to add the snapshot.

Storage Group lists all Storage Groups that are attached to the storage system. Any host assigned to that Storage Group will be able to access the snapshot.

The default value for Storage Group is None - no host can have access to the new snapshot. However, before you can access a snapshot, you must add the new snapshot to a Storage Group and connect a host to that Storage Group.

8. Click OK to create the snapshot.

The application creates the snapshot and, if the action is successful, does the following:

• Places an icon and description for the new snapshot in the Snapshots container associated with the snapshot’s source LUN. The format for the snapshot description is

snapshot name[host name; Lun X; Inactive]

where Inactive means the snapshot is not participating in a snapshot session.

• Adds the text, Snapshot Inactive, to the description for the snapshot’s source LUN. For example:

LUN 18 [0x12; RAID 1; host name; Snapshot Inactive]

where Snapshot Inactive means none of the snapshots on this source LUN have been activated.

If there is an active snapshot on the source LUN the text Snapshot Active appears next to the host name.

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Adding a Snapshot to a Storage GroupBefore accessing your snapshot data, the snapshot you map to a session must belong to a Storage Group and the Storage Group must connect to a host.

You must assign the snapshot to a Storage Group other than the Storage Group that holds the source LUN.

You must assign multiple snapshots, of the same source LUN, to different Storage Groups.

To Add a Snapshot toa Storage Group

If the host that will have access to the snapshot already connects to a Storage Group, add the snapshot to that Storage Group. If you create a new Storage Group for the snapshot and then connect the host to the new Storage Group, the host will be removed from the original Storage Group and will no longer have access to the LUNs in that Storage Group.


2. Double-click the icon for the storage system to which the snapshot belongs.

3. Double-click the icon for the SP that owns the snapshot source LUN.

4. Double-click the icon for the source LUN.

5. Double-click the icon for the Snapshots container.

6. Right-click the icon for the snapshot you want to add to a Storage Group, and then click Add to Storage Groups.

7. In Available Storage Groups, select the Storage Group to which you want to add the snapshot.

The Storage Group moves to Selected Storage Groups.

8. Click OK to add the snapshot to the Storage Group.

9. To connect a host to the Storage Group, right-click the Storage Group, and then click Connect Hosts.

The Connect Hosts to Storage dialog box opens.

To connect the host to the Storage Group, refer to Setting Up Access Logix, in EMC’s Navisphere Manager Administrator’s Guide.

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Creating Multiple SnapshotsWith SnapView version 1.3x (or higher), you can create up to eight snapshots per source LUN. All eight snapshots can be active at the same time but each snapshot must be activated to a different snapshot session.

The deactivate and activate functions allow you to change the focus of a snapshot from one session to another. For example, if you create eight snapshots and start three snapshot sessions for a single source LUN, you can activate three of your snapshots to the three sessions. The remaining five snapshots will be inactive.

To Create MultipleSnapshots

To create multiple snapshots per source LUN, refer to Creating a Snapshot on page 2-13 and repeat steps 1 through 8.

Multiple snapshots, of the same source LUN, must be assigned to different Storage Groups.

Activating a SnapshotThe activate function maps the snapshot to a snapshot session. The activate function on some operating systems, when administered from the admsnap host utility, will also scan the second hosts system buses for storage-system devices and determine if any device is part of a snapshot session.

To Activate aSnapshot


2. Double-click the icon for the storage system on which the source LUN resides, and then double-click the icon for the SP to which the source LUN belongs.

3. Double-click the icon for the source LUN on which the snapshot resides.

4. Double-click the Snapshot icon.

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5. Right-click the snapshot you want to activate, and then click Activate Snapshot.

The Activate Snapshot dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

6. In Available Sessions, select the snapshot session name that you want the snapshot to activate to.

7. Click OK to activate the snapshot to the snapshot session you selected.

If the action is successful, Navisphere closes the dialog box. Otherwise, Navisphere displays an error message and the dialog box remains open.

Depending on your operating system, additional steps may be required from the second host in order to make the snapshot visible to the operating system.

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Deactivating a SnapshotThe deactivate function unmaps a snapshot from a snapshot session. The snapshot and snapshot session still exist but are not visible from the second host.

The Navisphere Manager deactivate function does not flush all data and clear all buffers on the second host. To flush I/O from this host use the admsnap deactivate utility command on this host or any operating system specific commands to accomplish this task.

You must deactivate a snapshot before you can map it to another snapshot session. For example, if you start eight snapshot sessions and create one snapshot for a single source LUN, a second host can not activate another session until it deactivates from the current session. Once the second host deactivates the snapshot from the snapshot session, it can activate and deactivate between the eight sessions.

To Deactivate aSnapshot


2. Double-click the icon for the storage system on which the source LUN resides, and then double-click the icon for the SP to which the source LUN belongs.

3. Double-click the icon for the source LUN on which the snapshot resides.

4. Double-click the Snapshot icon.

5. Right-click the snapshot you want to deactivate, and then click Deactivate Snapshot. A message appears stating that you may need to flush I/O on the host operating system that is viewing the snapshot. If you click Cancel, no action is performed. If you click Yes, the snapshot you selected is deactivated from the snapshot session.

Depending on your operating system, additional steps may be required from the second host in order flush all data and clear all buffers on the second host.

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Destroying a SnapshotWhen you destroy a snapshot, the following is true:

◆ If the snapshot is inactive, only the snapshot selected will be destroyed.

◆ If the snapshot is active, an warning message appears indicating that the snapshot should be deactivated before it can be destroyed. If you accept the warning message the snapshot is deactivated, destroyed, and the following is true:

◆ If the snapshot belongs to one or more Storage Groups and you destroy the snapshot, the hosts connected to the Storage Groups will no longer have access to the destroyed snapshot.

To Destroy a Snapshot 1. Right-click the icon for the snapshot you want to destroy, and then click Destroy Snapshot.

2. In the confirmation dialog box, click Yes to destroy the snapshot.

The application removes the snapshot icon from the Snapshots container in the Storage tree.

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Starting a Snapshot SessionYou can start a snapshot session in either normal or simulation mode. A normal snapshot session stores both a copy of the unchanged LUN data and statistical data, such as the number of writes to the snapshot cache. A session started in simulation mode records only the statistical data.

Before starting a snapshot session, the SP cache must contain at least one LUN. See Destroying a Snapshot on page 2-19.

Normal Mode Snapshot Session

A normal snapshot session stores both a copy of the unchanged source LUN data and statistical data, such as the number of writes and reads to the snapshot cache. When a session is active, a host can read data from the snapshot.

To Start a Session inNormal Mode


2. Right-click the icon for the storage system on which you want to start the snapshot session, and click Start Snapshot Session.

If Start Snapshot Session appears dimmed and is unavailable, be sure there is at least one LUN in the SP’s snapshot cache, and that you have not exceeded the eight-session limit per source LUN.

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Starting a Snapshot Session 2-21


The Start Snapshot Session dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

3. In Session Name, enter a unique name for the snapshot session.

To agree with an admsnap requirement for a valid session name, include only characters, numbers, spaces, and underscores in Session Name. Symbols are not supported.

If you do not enter a unique name and then click OK, the software displays an error message.

4. In Source LUNs Available, select the Snapshot Source LUN Name on which to start the snapshot session.

If you start the session by right-clicking a storage-system icon, the list includes all source LUNs available on the storage system. If you start a session by right-clicking a source LUN icon, the list includes only the selected source LUN.

5. Click OK to start the session. If the action is successful, the application places an icon and the name of the session in the Snapshot Sessions container located beneath the session’s source LUN and the storage system in the Storage tree.

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On the second host, if you have installed the admsnap utility (supplied with the SnapView software), then use admsnap as follows to make the new session available for use.

On the second host, enter an admsnap -activate command as explained in the admsnap Host Management Utility Administrator’s Guide. On a Windows system, the admsnap command returns a drive letter that you can use immediately to access the snapshot data. On a UNIX system, the command returns a device name on which you must run fsck, and then mount to make a file system available for use.

If you have not installed admsnap, use Manager to activate a snapshot to a snapshot session, then you must reboot the second host or, using some other means, cause it to recognize the new device created when you started the snapshot session. Installing admsnap is explained in the Admsnap Host Management Utility Administrator’s Guide.

To stop a snapshot session, refer to Stopping a Snapshot Session on page 2-24.

Simulation Mode Snapshot Session

Starting a session in simulation mode helps you verify that you have correctly configured the size of the snapshot cache. Unlike a session run in normal mode, a session run in simulation mode does not store a copy of the unchanged source LUN data. It records only the statistical data, such as the number of writes to the snapshot cache that would have occurred had this not been a simulation. This data provides a reasonable approximation of how large the snapshot cache should be for this session. We recommend that you make the snapshot cache larger than required so that you do not run out of cache disk space.

While the session is running, use the Snapshot Session Properties dialog box to monitor the snapshot cache usage for the SP. (Refer Monitoring the Snapshot Cache Usage on page 4-3.)

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To Start a Session inSimulation Mode

1. Set up the session as you would a normal session — assign a name to the session, and select a snapshot LUN from the Source LUNs Available list.

2. In the Start Snapshot Session dialog box, be sure to select Simulation Mode.

3. Click OK to start the simulated session.

While the session is running, monitor the session to determine if the snapshot cache is the needed size. (Refer Monitoring the Snapshot Cache Usage on page 4-3)

Do not activate a snapshot to a session that is running in simulation mode.

Multiple Snapshot Sessions

With SnapView version 1.3x (or higher), you can start up to eight snapshot sessions per source LUN. Only one snapshot can be mapped to a particular session at a time. The deactivate and activate functions allow you to change the focus of a snapshot from one session to another. To activate a snapshot to a session, refer to Activating a Snapshot on page 2-16. To deactivate a snapshot from a session, refer to Deactivating a Snapshot on page 2-18.

To Start MultipleSnapshot Sessions

You can start multiple snapshot sessions in either normal or simulation mode. To start multiple snapshot sessions per source LUN, refer to Starting a Snapshot Session on page 2-20 and repeat the steps for the mode that you want your session to run.

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Stopping a Snapshot SessionStopping a session frees the snapshot cache LUN space used by the session and any SP memory used to maintain the session image. The newly freed snapshot cache space becomes available for other snapshot sessions.

If the snapshots participating in the session belong to one or more Storage Groups and you stop the snapshot session, the hosts connected to the Storage Groups will no longer have access to the snapshots in those Storage Groups. It is recommended that you do one of the following:

◆ Flush the I/O on the host viewing the active snapshot before stopping a snapshot session.

◆ Deactivate the snapshot before stopping the session.

Stopping a session with an active snapshot makes the snapshot appear inactive.

To Stop a SnapshotSession

To stop a snapshot session, do the following:

The time it takes to stop a snapshot session could be increased if that session belongs to a source LUN that is running multiple snapshot sessions. This is due to the cache having to determine which writes go with the session that has received the stop command.


2. Double-click the icon for the storage system on which the snapshot session is running, and double-click Snapshot Sessions.

3. Right-click the icon for the snapshot session you want to stop, and click Stop Session.

4. Click Yes to stop the session, or click No to continue the session.

Setting Up and Using SnapView Version 1.2x (or Lower) 3-1

3Invisible Body Tag

This chapter describes how to set up and use SnapView version 1.2x (or lower).

Determining your SnapView version - From the Enterprise Storage dialog box click the Storage tab; right-click the storage system icon; click Properties; click the Software tab; and, in the Packages list view the version of SnapView.

Major sections in this chapter are

◆ SnapView Requirements ...................................................................3-2◆ SnapView Operations Overview .....................................................3-3◆ Using SnapView .................................................................................3-7◆ Snapshot Cache ..................................................................................3-7◆ Creating a Snapshot......................................................................... 3-11◆ Starting a Snapshot Session ............................................................3-15

Setting Up and UsingSnapView

Version 1.2x (or Lower)

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Setting Up and Using SnapView Version 1.2x (or Lower)

SnapView RequirementsTo ensure that you have the most up-to-date information about the SnapView driver, EMC posts the release notes for this driver on the EMC Powerlink web site. We recommend that you download a copy of the release notes before you start the Manager software. To access EMC powerlink use the following url:


After you log in, select Services → Document Library → CLARiiON → CLARiiON Fibre Channel Storage → CLARiiON FC Software, and find the EMC SnapView and Admsnap Release Notes (P/N 085090552).

SnapView has the following requirements:

◆ Any FC4700 Storage System that you want to manage, must have SnapView installed.

◆ Access Logix must be installed on the same FC4700 Storage System that is running SnapView.

◆ The snapshot cache must be established on one or more LUNs that do not belong to any Storage Group.

◆ The source and the cache LUNs must be owned by the same SP.

◆ You can use the snapshot in only one session at a time.

◆ The source LUN and snapshot must be assigned to different Storage Groups. The source LUN Storage Group should be accessible to the production host and the snapshot Storage Group to the other host.

Setting Up SnapView Version 1.2x (or Lower)Before starting a snapshot session, you must complete the following tasks:

◆ Make sure that you have bound LUNs available for the snapshot cache. See Binding LUNs for the Snapshot Cache on page 3-7.

◆ Create snapshots and assign the snapshots to Storage Groups. See Creating a Snapshot on page 3-11.

◆ Configure the snapshot cache. See Configuring an SP’s Snapshot Cache on page 3-8.


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SnapView Operations Overview The section is an overview of the operations you need to perform when using SnapView version 1.2x (or lower).

1. On an SP determine how many source LUNs you want a snapshot of. The size of these LUNs will help you decide on an approximate snapshot cache size.

The LUN(s) in the snapshot cache are needed to store the original data when that data is first modified on the source LUN(s). The snapshot cache can use any public LUN that is not part of any Storage Group. (This requires forethought, since normally you assign each LUN that will store user data to a Storage Group.)

The snapshot cache pool should be large enough for all concurrent sessions on that SP. This is why an adequate snapshot cache size is essential. If you run out of cache space while a snapshot session is running, your session will be destroyed.

A general guideline for snapshot cache size is 10% of the size of the LUN you want to copy; however, you may want to use a larger cache size, such as 20%, 50%, or even 100%. SnapView has a simulation mode option to help you determine an ideal snapshot cache size. See Simulation Mode Snapshot Session on page 3-17.

2. On the storage system, bind one or more LUNs for each SP to the size you determined for the snapshot cache.

3. On the storage system that owns the source LUN, allocate the snapshot cache.

You allocate LUNs to the snapshot cache using the Manager Snapshot Cache Properties dialog box.

The snapshot cache pool is shared by all the active sessions on a specific SP. If the snapshot cache size is too small, you can add an additional LUN to the snapshot cache pool or terminate a session to free its cache space. If the snapshot cache fills up, SnapView terminates the session that encountered the error, logs an error, and releases the snapshot cache space used by that session.

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When you allocate the snapshot cache, you specify a cache chunk size. The chunk size is the size of each snapshot cache write. With the default chunk size of 128 Kbytes, the software divides the source LUN into 128-Kbyte blocks and, if any part of a 128-Kbyte block is changed during the session, the software retains the original image of that block in the snapshot cache. The chunk size applies to both SPs. You can change the chunk size after you allocate the cache if there are no active snapshot sessions running on the storage system.

4. On the storage system, create the snapshot.

A snapshot occupies no disk space and is accessible only for the duration of the snapshot session. To create a snapshot, use Navisphere Manager or CLI.

You must assign the snapshot to a Storage Group other than the Storage Group that holds the source LUN. Make sure that the snapshot Storage Group is accessible by the second host. Navisphere Manager will prompt you for this. This step is needed only once.

5. On the second host, identify the snapshot to the operating system. This procedure depends on the operating system; for example, with Windows you need to run Disk Admin. This step is needed only once, as part of the SnapView initial setup.

6. On the storage system that owns the source LUN, start a snapshot session.

You can start a snapshot session using the Navisphere Manager Start Snapshot Session function or the admsnap start operation.

The session name identifies the session. You create the name when you start a snapshot session, use it to activate the snapshot, and then use it to stop the session.

7. On the second host, if you have installed the admsnap utility (supplied with the SnapView software), then use admsnap as follows to make the new session available.

On the second host, enter an admsnap activate command as explained in the Admsnap Host Management Utility Administrator’s Guide. On a Windows system, the admsnap command returns a drive letter that you can use immediately to access the snapshot data. On a UNIX system, the command returns a device name on which you must run fsck and then mount to make a file system available for use.

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If you have not installed admsnap, then you must reboot the second host or, using some other means, cause it to recognize the new device created when you started the snapshot session. Installing admsnap is explained in the Admsnap Host Management Utility Administrator’s Guide.

8. On the second host, use the backup host’s snapshot data as desired for modeling, testing, or backup. As needed, mount any file systems or start database software to analyze the snapshot data or back it up.

9. Before stopping the snapshot session, make the snapshot session unavailable to the second host by doing one of the following:

• Use the admsnap deactivate command as explained in the Admsnap Host Management Utility Administrator’s Guide.

• UNIX server - use the umount command.

10. On the storage system that owns the source LUN, stop the snapshot session.

You can stop the session using Manager, CLI or admsnap. Stopping a session frees the snapshot cache space and any SP memory used for the session. The newly freed snapshot cache space becomes available for other snapshot sessions.

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Snapshot Session Overview

The following figure shows how a snapshot session starts, runs, and stops.

In the following figure, the production host and source LUN are in one Storage Group. The second host and snapshot are in another Storage Group

Figure 3-1 How a Snapshot Session Starts, Runs, and Stops

EMC1823

ProductionHost

SecondHost

SourceLUN

SnapshotSnapshotcache

1. Before session starts

SourceLUN

SnapshotCache

ProductionHost

SecondHost

2. Start session (2:00 p.m.)

SourceLUN

SnapshotCache

ProductionHost

SecondHost

5. Stop session (4:25 p.m.)4. End operation (4:15 p.m.)

ProductionHost

SecondHost

SourceLUN


Cache

3. Begin operation, suchas back-up or decisionsupport (2:02 p.m.)

Productionhost

Secondhost

SourceLUN


Cache

Changed chunkson source LUN

Unchanged chunks incache and snapshot

Unchanged chunkson source LUN

Key:

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Using SnapView 3-7


Using SnapViewWith Navisphere Manager you can use SnapView to:

◆ Create a snapshot (see Creating a Snapshot on page 3-11)

◆ Start and stop a snapshot session (see Starting a Snapshot Session on page 3-15 and Stopping a Snapshot Session on page 3-18)

◆ Display the status and properties of the snapshot cache, snapshot sessions, and snapshots (see Chapter 4, Displaying SnapView Properties)

If the MirrorView option is installed, we recommend that you do not take a snapshot of the remote mirror secondary copy while the secondary copy is being synchronized. The data may not be useful.

Snapshot CacheFor SnapView version 1.2x (or lower), snapshot cache LUNs are dedicated on a per SP basis. The SP manages the snapshot cache space and apportions it to all snapshot sessions running on that SP. For example, if SP A contains three snapshot sessions running on three different source LUNs, all three of these snapshot sessions will allocate snapshot cache space from the same snapshot cache LUN.

If you intend to create snapshots for LUNs owned by SP A and LUNs owned by SP B, configure the snapshot cache for each SP, as described in Configuring an SP’s Snapshot Cache on page 3-8.

Binding LUNs for the Snapshot CacheBefore binding LUNs for the snapshot cache, think about which source LUNs will participate in a snapshot session. The size of these LUNs will help you determine an approximate snapshot cache size. To bind LUNs, refer to the section Creating LUNs on RAID Groups, in EMC’s Navisphere Manager Version 5.X Administrator’s Guide.

The snapshot cache must be established on one or more LUNs that do not belong to any Storage Group.

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Snapshot Cache SizeAn adequate snapshot cache size is essential because if the snapshot cache fills up (runs out of space), the session that is trying to allocate cache from the SP cache pool will be terminated.

Since the snapshot cache stores only blocks of the source LUN’s original data when that data is first updated on the source LUN, a general guideline for snapshot cache size is 10% of the size of the LUN you want to copy. For example, if the LUN you want to copy belongs to SP A and is 10 Gbytes in size, you will need a snapshot cache size of at least 1 Gbyte for SP A. Stopping a session (or having one terminated) frees the associated snapshot cache space, so if you are near the limit and there is one snapshot session that is less important to you than another, you can terminate the less important session to free snapshot cache space for the more important ones.

You can also run a snapshot session in simulation mode (see page 3-17) to help you determine a suitable snapshot cache size. If you determine that the snapshot cache size is too small, you can add LUNs to the snapshot cache, as described in the next section, Configuring an SP’s Snapshot Cache.

If you intend to write to the snapshot, make sure that the snapshot cache is large enough to store these writes, since all writes to the snapshot are stored in the snapshot cache.

Configuring an SP’s Snapshot Cache

The snapshot cache consists of one or more private LUNs, and the size of the snapshot cache is the aggregate of all these LUNs. The LUNs in the snapshot cache are needed to store blocks of the original data when that data is first updated on the source LUN. For any one snapshot session, the contents of the snapshot cache and any unchanged source LUN blocks comprise the snapshot. The SP that owns the snapshot source LUN must own the snapshot cache LUNs. The SP manages the snapshot cache space and apportions it to all source LUNs that are involved in a snapshot session.

Each SP has its own snapshot cache, and before starting a snapshot session, the snapshot cache must contain at least one LUN. You can increase or decrease the size of the snapshot cache by adding or removing LUNs.

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Snapshot Cache 3-9


If several snapshot sessions are running on an SP, and you determine that the snapshot cache size is running out of space, you can terminate a session to free its cache space, or you can add LUNs to the snapshot cache while the session is active. If the snapshot cache fills up, the software automatically terminates the session that encountered the error, logs an error, and releases the snapshot cache space used by that session. At this point, the snapshot becomes inactive and any host that has mounted volumes on the snapshot will receive I/O errors and lose access.

To Configure an SP’sSnapshot Cache

If you plan to create snapshots for LUNs owned by SP A and LUNs owned by SP B, configure the snapshot cache for each SP.


2. Double-click the icon for the storage system for which you want to configure the snapshot cache, and double-click Snapshot Cache.

3. Right-click either the SP A or SP B cache icon, and click Properties.

The Snapshot Cache Properties dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

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4. In Chunk Size (Blocks), select the chunk size (size of each snapshot cache write) for both SPs.

5. In Available LUNs, select the LUNs that you want to add to the snapshot cache for each SP.

Available LUNs lists only those LUNs that are eligible for inclusion in the snapshot cache.

If there are no LUNs in the list or if none of the available LUNs are the necessary size, you must bind new LUNs and then add them to the snapshot cache. To bind LUNs refer to the section Creating LUNs on RAID Groups, in EMC’s Navisphere Manager Administrator’s Guide.

6. To add the selected LUNs to SP A’s snapshot cache, click Add to SP A Cache; to add the LUNs to SP B’s cache, click Add to SP B Cache.

The selected LUNs move to the SP Cache Member LUNs list for SP A or SP B, and the value in Modified Capacity is updated to reflect the changes.

Modified Capacity is the current size of the SP’s snapshot cache.

7. To remove LUNs from the SP Cache Member LUNs list, select the LUNs you want to remove, and then click Remove from Cache.

If there are any snapshot sessions running on either SP, you cannot remove any LUNs from the cache.

8. When you have added all the LUNs you want to the snapshot cache, click OK to apply the changes and close the dialog box.

The snapshot cache LUNs are added to either the SP A Cache or SP B Cache container in the Storage tree.

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Creating a SnapshotA snapshot is a composite of the source LUN and snapshot cache data that lasts only as long as the snapshot session. Each snapshot is linked to a source LUN. If the storage system loses power while the session is running, the snapshot is lost.

To Create a Snapshot 1. In the Enterprise Storage dialog box, click the Storage tab.

2. Double-click the icon for the storage system on which the source LUN resides.

3. Double-click the icon for the SP to which the source LUN belongs.

4. Right-click the icon for the source LUN, and then click Create Snapshot.

The Create Snapshot dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

5. In Storage System and Snapshot Source LUN, verify that you are creating the snapshot for the correct source LUN on the correct storage system.

6. In Snapshot Name, enter a unique name for the snapshot. If the Snapshot Name is left blank, the default name SCLUN 0xn is assigned to the snapshot, where n is an incremental internal number that is assigned to the snapshot.

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If you enter an invalid name and then click OK, the application displays an error message.

7. In Storage Group, select the Storage Group to which you want to add the snapshot.

For shared storage systems, Storage Group lists all Storage Groups that are attached to the storage system. Any host assigned to that Storage Group will be able to access the snapshot.

The default value for Storage Group is None - no host can have access to the new snapshot. However, before you can access a snapshot, you must add the new snapshot to a Storage Group and connect a host to the Storage Group.

8. Click OK to create the snapshot.

The application creates the snapshot and, if the action is successful, does the following:

• Places an icon and description for the new snapshot in the Snapshots container associated with the snapshot’s source LUN. The format for the snapshot description is

snapshot name[Lun X; Inactive]

where Inactive means the LUN is not participating in a snapshot session.

• Adds the text, Snapshot Inactive, to the description for the snapshot’s source LUN. For example:

LUN 18 [0x12; RAID 1; Snapshot Inactive]

where Snapshot Inactive means the source LUN is not participating in a snapshot session.

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Adding a Snapshot to a Storage GroupBefore starting a snapshot session, the snapshot must belong to a Storage Group and the Storage Group must connect to a host.

You must assign the snapshot to a Storage Group other than the Storage Group that holds the source LUN.

To Add a Snapshot toa Storage Group

If the host that will have access to the snapshot already connects to a Storage Group, add the snapshot to that Storage Group. If you create a new Storage Group for the snapshot and then connect the host to the new Storage Group, the host will be removed from the original Storage Group and will no longer have access to the LUNs in that Storage Group.


2. Double-click the icon for the storage system to which the snapshot belongs.

3. Double-click the icon for the SP that owns the snapshot source LUN.

4. Double-click the icon for the source LUN.

5. Double-click the icon for the Snapshots container.

6. Right-click the icon for the snapshot you want to add to a Storage Group, and then click Add to Storage Groups.

7. In Available Storage Groups, select the Storage Group to which you want to add the snapshot.

The Storage Group moves to Selected Storage Groups.

8. Click OK to add the snapshot to the Storage Group.

9. To connect a host to the Storage Group, right-click the Storage Group, and then click Connect Hosts.

The Connect Hosts to Storage dialog box opens. To connect the host to the Storage Group, refer to Setting Up Access Logix, in EMC’s Navisphere Manager Version 5.X Administrator’s Guide.

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Destroying a SnapshotWhen you destroy a snapshot, the following is true:

◆ If the snapshot is active, the application stops the session prior to destroying the snapshot, and both the session and snapshot are destroyed.

◆ If the snapshot belongs to one or more Storage Groups and you destroy the snapshot, the hosts connected to the Storage Groups will no longer have access to the destroyed snapshot.

To Destroy a Snapshot 1. Right-click the icon for the snapshot you want to destroy, and then click Destroy Snapshot.

2. In the confirmation dialog box, click Yes to destroy the snapshot.

The application removes the snapshot icon from the Snapshots container in the Storage tree.

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Starting a Snapshot SessionYou can start a snapshot session in either normal or simulation mode. A normal snapshot session stores both a copy of the unchanged LUN data and statistical data, such as the number of writes to the snapshot cache. A session started in simulation mode records only the statistical data.

Before starting a snapshot session, the following must be true:

◆ You must create a snapshot before starting a snapshot session.

◆ The snapshot should belong to a Storage Group and the Storage Group must connect to a host.

◆ The SP cache must contain at least one LUN. See Adding a Snapshot to a Storage Group on page 3-13.

A snapshot is accessible for only as long as the snapshot session lasts. If a the storage system loses power while the session is running, the snapshot is lost.

Normal Mode Snapshot Session

A normal snapshot session stores both a copy of the unchanged source LUN data and statistical data, such as the number of writes and reads to the snapshot cache. When a session is active, a host can read data from the snapshot.

To Start a Session inNormal Mode


2. Right-click the icon for the storage system on which you want to start the snapshot session, and click Start Snapshot Session.

If Start Snapshot Session appears dimmed and is unavailable, be sure there is at least one LUN in the SP’s snapshot cache and that a snapshot has been created.

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The Start Snapshot Session dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

3. In Session Name, enter a unique name for the snapshot session.

To agree with an admsnap requirement for a valid session name, include only characters, numbers, spaces, and underscores in Session Name. Symbols are not supported.

If you do not enter a unique name and then click OK, the software displays an error message.

4. In Snapshots Available, select the LUNs that you want to participate in the snapshot session.

If you start the session by right-clicking a storage-system icon, the list includes all available snapshots on the storage system. If you start a session by right-clicking a snapshot icon, the list includes only that snapshot.

5. Click OK to start the session, and if the action is successful, the application does the following:

• Places an icon and description for the active snapshot session in the Snapshot Sessions container in the Storage tree.

• Places an icon and description for each snapshot participating in the session under the icon for the active snapshot session.

3



• Changes the status of the participating snapshot and source LUN from Inactive to Active in the Storage tree.

On the second host, if you have installed the admsnap utility (supplied with the SnapView software), then use admsnap as follows to make the new session available for use.

On the second host, enter an admsnap -activate command as explained in the admsnap Host Management Utility Administrator’s Guide. On a Windows system, the admsnap command returns a drive letter that you can use immediately to access the snapshot data. On a UNIX system, the command returns a device name on which you must run fsck, and then mount to make a file system available for use.

If you have not installed admsnap, then you must reboot the second host or, using some other means, cause it to recognize the new device created when you started the snapshot session. Installing admsnap is explained in the admsnap Host Management Utility Administrator’s Guide.

To stop a snapshot session, refer to Stopping a Snapshot Session on page 3-18.

Simulation Mode Snapshot Session Starting a session in simulation mode helps you verify that you have correctly configured the size of the snapshot cache. Unlike a session run in normal mode, a session run in simulation mode does not store a copy of the unchanged source LUN data. It records only the statistical data, such as the number of writes to the snapshot cache that would have occurred had this not been a simulation. This data provides a reasonable approximation of how large the snapshot cache should be for this session. We recommend that you make the snapshot cache larger than required so that you do not run out of cache disk space.

While the session is running, use the Snapshot Session Properties dialog box to monitor the snapshot cache usage for the SP. (Refer Monitoring the Snapshot Cache Usage on page 4-3)

3



To Start a Session inSimulation Mode

1. Set up the session as you would a normal session — assign a name to the session, and select LUNs from the Snapshots Available list.

2. In the Start Snapshot Session dialog box, be sure to select Simulation Mode.

3. Click OK to start the simulated session.

While the session is running, monitor the session to determine if the snapshot cache is the needed size. (Refer to Monitoring the Snapshot Cache Usage on page 4-3)

Stopping a Snapshot SessionStopping a session frees the snapshot cache LUN space used by the session and any SP memory used to maintain the session image. The newly freed snapshot cache space becomes available for other snapshot sessions. Stopping a session also makes the snapshot appear inactive.

If the snapshots participating in the session belong to one or more Storage Groups and you stop the snapshot session, the hosts connected to the Storage Groups will no longer have access to the snapshots in those Storage Groups.

To Stop a SnapshotSession


2. Double-click the icon for the storage system on which the snapshot session is running, and double-click Snapshot Sessions.

3. Right-click the icon for the snapshot session you want to stop, and click Stop Session.

4. Click Yes to stop the session, or click No to continue the session.

Displaying SnapView Properties 4-1

4Invisible Body Tag

This chapter describes how to display the Properties dialog box for each SnapView component.

Major sections are

◆ Displaying SnapView Properties .....................................................4-2◆ Displaying Status of All Snapshots and Snapshot Sessions ........4-5

Displaying SnapViewProperties

4


Displaying SnapView Properties

Displaying SnapView PropertiesEach snapshot, snapshot cache, and snapshot session has a Properties dialog box associated with it that provides a variety of information about the component. This section describes how to open the Properties dialog box for each component and view the component’s properties.

Snapshot Properties To display the properties of a snapshot, do the following:


2. Double-click the storage system and SP in which the snapshot resides.

3. Double-click the source LUN in which the snapshot resides.

4. Double-click the Snapshot container.

5. Right-click the snapshot icon for which you want to display properties, and click Properties. The Snapshot Properties dialog box opens. For information on the properties in the dialog box, click Help.

4

Displaying SnapView Properties 4-3


Snapshot CacheProperties

To display the properties of the snapshot cache, do the following:


2. Double-click the storage system in which the snapshot cache resides.

3. Double-click the Snapshot Cache icon.

4. Right-click SP A Cache or SP B Cache, and click Properties.The Snapshot Cache Properties dialog box opens. For information on properties in the dialog box, click Help.

Monitoring the Snapshot Cache Usage

To help determine if the snapshot cache is the necessary size, do the following:

1. In the Snapshot Cache dialog box, select the Allocation tab to check the value for Session Usage for SP A or SP B (%).

If the SP usage registers at 80% to 90%, you may want to increase the size of the snapshot cache. (For SnapView version 1.2x (or lower), see Adding a Snapshot to a Storage Group on page 3-13. For SnapView version 1.3x (or higher), see Configuring an SP’s Snapshot Cache on page 2-10.)

2. To display a list of all LUNs participating in this session, click the Member LUNs tab.

3. Click Close to close the dialog box.

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Snapshot SessionProperties

You can view statistics, such as total reads and writes, for an active session. You can also monitor the snapshot cache usage for the SPs and determine if the snapshot cache is the necessary size.


2. Double-click the icon for the storage system in which the snapshot session is running.

3. Double-click the Snapshot Sessions icon.

4. Right-click the icon for the session you want to monitor, and click Properties.

The Snapshot Session Properties dialog box opens, similar to the following. For information on the properties in the dialog box, click Help.

5. To display the statistics for this session, click the Statistics tab.

4

Displaying Status of All Snapshots and Snapshot Sessions 4-5


Displaying Status of All Snapshots and Snapshot SessionsYou can view the status of all snapshots on all managed storage systems as well as the status of all snapshot sessions.

On the Operations menu in the Main window, click SnapView Summary.

The SnapView Summary dialog box opens, similar to the following. For information on the properties in the Snapshots tab, click Help.

To Display Status for all Snapshots

In the SnapView Summary dialog box, click the Snapshots tab. For information on the properties in the Snapshots tab, click Help.

To Display Status for all Snapshot Sessions

In the SnapView Summary dialog box, click the Sessions tab. For information on the properties in the Sessions tab, click Help.

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EMC SnapView Administrator’s Guide for Navisphere 5.X g-1

Glossary

This glossary contains terms related to SnapView. Many of these terms are used in this manual.

AActive A snapshot is currently participating in a snapshot session and is

accessible to secondary hosts.

Activate An operation on a snapshot that maps it to a snapshot session. This feature is available in Manager only with Snapview version 1.3x or higher. Refer to page 2-1 or page 3-1 to determine the version of SnapView running in the system you are managing.

Admsnap Host-based software that provides a command line interface to SnapView software running in a storage-system SP. With admsnap, you can start and stop sessions and activate and deactivate snapshots using commands typed on a second host system.

CChunk An aggregate of multiple disk blocks used by SnapView to perform

CopyOnFirstWrite operations. The selectable chunk sizes are 16K, 32K, 64K, 128K, 256K, and 512K. The default size is 128K.

g-2 EMC SnapView Administrator’s Guide for Navisphere 5.X

Glossary

CopyOnFirstWrite(COFW)

An algorithm that copies current contents of a source LUN before it is modified (written to). The COFW operation is on a chunk: before the first modification of any disk blocks within a chunk, the original data of the chunk is read and stored in the snapshot cache. This policy only applies to the first modification of the data. Overwrite of any data that has already had a COFW does not require any extra processing since the original data was previously saved in the snapshot cache.

DDeactivate An operation on a snapshot that unmaps it from a snapshot session to

make it invisible to any secondary hosts. The snapshot and snapshot session still exist. This feature is available only with SnapView version 1.3x or higher. Refer to page 2-1 or page 3-1 to determine the version of SnapView running in the system you are managing.

IInactive The snapshot is not currently participating in a snapshot session and

is invisible to any secondary hosts.

PPoint-in-Time The moment the snapshot session starts.

Private LUN A LUN that cannot be assigned to a storage group. Once a LUN is added to the snapshot cache it becomes a private LUN.

SSnapshot A point-in-time image of a source LUN. A snapshot occupies no disk

space, but appears like a normal LUN to secondary hosts and can serve for backup or another use.

Other, older terms for snapshot, which are no longer used, include SnapshotCopy LUN (SCLUN) and SnapCopy LUN (SLU).

Snapshot Cache The disk storage used to hold the original data from a source LUN that has been modified since the start of a snapshot session. This storage is pre-allocated and is shared by all snapshot sessions on an SP. The snapshot cache can consist of multiple logical units, which are managed as a pool of space.

EMC SnapView Administrator’s Guide for Navisphere 5.X g-3

Glossary

Snapshot Cache LUN A logical unit (LU) that is assigned to the SnapView cache. The cache LUNs must be located on the same SP as the source LUNs and must be exclusively used for snapshot purposes (private LUN). For more information on how the caching model works and how to determine the size of the snapshot cache, refer to the Snapshot Cache section for the version of SnapView you are running. (Refer to page 2-1 or page 3-1 to determine the version of SnapView running in the system you are managing.)

Snapshot Session The period of time that SnapView is managing a snapshot cache region. The snapshot session begins when you start a session using Manager, CLI, or admsnap and ends when you stop the session. You can give each snapshot session a name (the snapshot session name) when you start the session. The name persists throughout the snapshot session and is viewable through Navisphere. You use the name to check session status and to end the session.

SnapView A feature of FC4700 storage systems that allows you to obtain a snapshot of a LUN at a given point in time. The snapshot can serve for backup, decision support scenarios, or as a base for temporary operations on the production data without damaging the original data on the source LUN.

Source LUN Term used to define the original LUN from which a snapshot is generated from. An older term for source LUN, which is no longer used, is Target LUN (TLU).

g-4 EMC SnapView Administrator’s Guide for Navisphere 5.X

Glossary

EMC SnapView Administrator’s Guide for Navisphere 5.X i-1

Aactivate snapshot

SnapView Version 1.3x (or higher) 2-16, 2-18admsnap command 2-22

SnapView Version 1.2x (or lower) 3-4, 3-17SnapView Version 1.3x (or higher) 2-6, 2-22

Bbinding snapshot cache LUNs

SnapView Version 1.2x (or lower) 3-7SnapView Version 1.3x (or higher) 2-9

Ccache

configuring SP snapshot cacheSnapView Version 1.2x (or lower) 3-8SnapView Version 1.3x (or higher) 2-10

snapshot cache sizeSnapView Version 1.2x (or lower) 3-8SnapView Version 1.3x (or higher) 2-9

configuration guidlinesSnapView Version 1.3x (or higher) 2-3

Create Snapshot dialog boxSnapView Version 1.2x (or lower) 3-11SnapView Version 1.3x (or higher) 2-13

Ddeactivate snapshot

SnapView Version 1.3x (or higher) 2-16, 2-18

dialog boxesCreate Snapshot


Start Snapshot SessionSnapView Version 1.2x (or lower) 3-16SnapView Version 1.3x (or higher) 2-21

Mmultiple snapshots

SnapView Version 1.3x (or higher) 2-16

Ssnapshot cache

binding LUNsSnapView Version 1.2x (or lower) 3-7SnapView Version 1.3x (or higher) 2-9

displaying properties 4-3snapshot session

displaying properties 4-4monitoring 4-4starting


starting in simulation modeSnapView Version 1.2x (or lower) 3-17SnapView Version 1.3x (or higher) 2-22

starting multipleSnapView Version 1.3x (or higher) 2-23

stoppingSnapView Version 1.2x (or lower) 3-18SnapView Version 1.3x (or higher) 2-24

Index

EMC SnapView Administrator’s Guide for Navisphere 5.Xi-2

Index

snapshotsactivate

SnapView Version 1.3x (or higher) 2-16creating


creating multipleSnapView Version 1.3x (or higher) 2-16

deactivateSnapView Version 1.3x (or higher) 2-16

destroyingSnapView Version 1.2x (or lower) 3-14SnapView Version 1.3x (or higher) 2-19

display properties 4-2SnapView

displaycomponent status 4-2snapshot cache properties 4-3snapshot properties 4-2snapshot session properties 4-4

SnapView Version 1.2x (or lower)admsnap command 3-4, 3-17binding snapshot cache LUNs 3-7configuring SP snapshot cache 3-8creating snapshots 3-11destroying a snapshot 3-14requirements 3-2setting up 3-2snapshot cache size 3-8starting a snapshot session 3-15starting a snapshot session, simulation mode

3-17stopping a snapshot session 3-18

SnapView Version 1.3x (or higher)activate snapshot 2-16admsnap command 2-6, 2-22binding snapshot cache LUNs 2-9configuring SP snapshot cache 2-10creating multiple snapshots 2-16creating snapshots 2-13deactivate snapshot 2-16destroying a snapshot 2-19requirements 2-2setting up 2-2snapshot cache size 2-9starting a snapshot session 2-20

starting a snapshot session, simulation mode 2-22

starting multiple snapshot sessions 2-23stopping a snapshot session 2-24

Start Snapshot Session dialog boxSnapView Version 1.2x (or lower) 3-16SnapView Version 1.3x (or higher) 2-21

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