VERITAS Volume Manager 4.1 Administrator's Guide

Administering Volumes
Backing up Volumes Online
Chapter 8 307
Backing up Volumes Online
It is important to make backup copies of your volumes. These provide
replicas of the data as it existed at the time of the backup. Backup copies
are used to restore volumes lost due to disk failure, or data destroyed due
to human error. VxVM allows you to back up volumes online with
minimal interruption to users.
Two methods of backing up volumes online are described in the following
sections: “Backing Up Volumes Online Using Mirrors” on page 307 and
“Backing Up Volumes Online Using Snapshots” on page 308. For
information on implementing off-host online backup, see Chapter 11,
“Configuring Off-Host Processing,” on page 383.
Backing Up Volumes Online Using Mirrors
If a volume is mirrored, it can be backed up by taking one of the data
plexes offline for a period of time. This removes the need for extra disk
space for the purpose of backup only. However, if the volume only has two
data plexes, it also removes redundancy of the volume for the duration of
the time needed for the backup to take place.
You can perform backup of a mirrored volume on an active system with
these steps:
Step 1. Dissociate one of the volume’s data plexes (vol01-01, for example) using
the following command:
# vxplex [-g diskgroup] dis plex
Optionally, stop user activity during this time to improve the consistency
of the backup.
Step 2. Create a temporary volume, tempvol, that uses the dissociated plex,
using the following command:
# vxmake -g diskgroup -U gen vol tempvol plex=plex
Step 3. Start the temporary volume, using the following command:
# vxvol [-g diskgroup] start tempvol