Seagate ST39175LW Betriebsanweisung PDF herunterladen (Seite 20)

Frozen Image Overview

10 NetBackup ServerFree Agent System Administrator’s Guide

Frozen Image Overview

Large active databases available around-the-clock are difficult to back up without

incurring a penalty. Often, the penalty takes one of two forms:

◆ The entire database is taken offline to allow time for the data copy, resulting in

suspension of service and inconvenience to users.

◆ The copy is made very quickly but produces an incomplete version of the data, some

transactions having failed to complete.

The basic method of solving this problem is called a frozen image. This means “capturing”

the data (such as a file system) at a particular instant, without causing significant

downtime. The resulting capture or image can then be backed up without affecting the

performance or availability of the application or database server. Without a complete,

up-to-date image of the data, a correct backup cannot be obtained.

Figure 2. Creating a frozen image for backup

Figure 2

represents the creation of a frozen image; on a typical online system, several such

images might be created within a 24-hour period.

When a backup is managed by a backup agent on a Fibre Channel network, the data to

back up must be contained in a frozen image. This is because the backup agent on the

network is unable to determine whether the data is currently being changed by another

application. If the data is captured as a frozen image, NetBackup can correctly map the

data to absolute physical addresses. Once the data is correctly mapped, it is ready to be

backed up.

Two types of frozen image methods are available, both supported by NetBackup

ServerFree Agent: copy-on-write snapshots and mirrors.

Source data: busy system

with nonstop transactions

Image is “frozen” and

sent to a backup agent

(such as a third-party

copy device) for

backup.

Time . . .

Frozen image

Backup agent

Fibre

Channel

NetBackup client

NetBackup 4.0V ServerFree Agent System Administrator's Guide for Solaris

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 103 104

Keine Kommentare

Seagate ST39175LW Betriebsanweisung Seite 20