Seagate ST39175LW Instrukcja Naprawy Pobierz pdf (Strona 31)

Chapter 1, Introduction 17

Frozen Image Overview

Since mirroring requires an exact, complete copy of the primary on a separate device

(equal in size to the disk being mirrored), it consumes more disk space than a

copy-on-write snapshot.

In NetBackup ServerFree Agent, the following frozen image methods support mirror

frozen images:

◆ vxvm (part of the Core Frozen Image Services option)

◆ TimeFinder (for EMC disk arrays; part of the Extended Frozen Image Services option)

◆ ShadowImage (for Hitachi disk arrays; part of the Extended Frozen Image Services

option)

◆ BusinessCopy (for HP disk arrays; part of the Extended Frozen Image Services

option)

For basic configuration instructions, and details on vxvm, refer to the “NetBackup

Configuration” chapter. For details on TimeFinder, ShadowImage, and BusinessCopy,

refer to the chapter titled “Extended Frozen Image Services (Array Integration Option).”

Snapshot vs. Mirror: Which to Choose?

Benefits of copy-on-write snapshot:

◆ Consumes less disk space: no need for secondary disks containing complete copies of

source data.

◆ Easier to configure.

Note If cost of the additional disk drives needed for mirroring is prohibitive, choose a

copy-on-write snapshot frozen image method (nbu_snap or fsclone). See usage

considerations under “Configuration Tips” in the chapter titled “NetBackup

Configuration.”

Benefits of mirror:

◆ Has less impact on the performance of the application or database host being backed

up (NetBackup client), because there is no need to run the copy-on-write mechanism.

◆ Allows faster backups: the backup process reads data from a separate disk (mirror)

operating independently of the primary disk that holds the client’s source data. This

means that, unlike the copy-on-write snapshot, there is no need to share disk I/O with

other processes or applications. Apart from NetBackup, no other applications have

access to the mirror disk. During a copy-on-write snapshot, the source data can be

accessed by other applications as well as by the copy-on-write mechanism, causing

disk I/O delays.

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Seagate ST39175LW Instrukcja Naprawy Strona 31