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Chapter 7, Extended Frozen Image Services (Array Integration Option) 117

Best Practices

Backup Policies in Conflict: Two Backups Accessing Same Volume

The above diagram shows /dev/vx/rdsk/dg/vol_1 on a single disk. The same conflict

will occur if /vol_1 is distributed across two or more disks.

To avoid this conflict, see “Avoiding Concurrent Access Conflicts” later in this chapter.

Concurrent Access to Volume Manager Volumes on Same Disks

A conflict can occur if two or more concurrent backups using Extended Frozen Image

Services attempt to access Volume Manager volumes that are distributed across the same

disks.

VERITAS Volume Manager (VxVM) supports three means of distributing volumes across

disks: striping, concatenating, and RAID5 (described in the Volume Manager

documentation). Use of these distribution methods can lead to access problems for

NetBackup Extended Frozen Image Services. The following diagram shows two VxVM

volumes, /dev/vx/rdsk/dg/vol_1 and /dev/vx/rdsk/dg/vol_2. Each is

distributed across two disks in an array (using any of the three distribution methods). If

two backups request frozen images of these volumes at the same time, a conflict occurs,

even though the two backups are attempting to access different volumes. This happens

because the Extended Frozen Image Services frozen image methods split the mirror disk

from the primary disk at the disk device layer, not at the volume layer.

Backup policy A

File list:

/dev/vx/rdsk/dg/vol_1

Backup policy B

File list:

/dev/vx/rdsk/dg/vol_1

Backup policy A starts job to back up /vol_1; mirror is locked to make

frozen image. Backup policy B attempts to back up /vol_1 and

requests frozen image: mirror is already locked—access denied.

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Seagate ST39175LW Guia de Resolução de Problemas Página 131