VERITAS Volume Manager 3.1 Administrator's Guide

Volume Tasks
Preparing a Volume to Restore From Backup
Chapter 6 255
Preparing a Volume to Restore From Backup
It is important to make backup copies of your volumes. This provides a
copy of the data as it stands 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. The Volume Manager allows you to back up volumes with
minimal interruption to users.
To back up a volume with the vxassist command, use the following
procedure:
Step 1. Create a snapshot mirror of the volume to be backed up.
The vxassist snapstart task creates a write-only backup mirror, which
is attached to and synchronized with the volume to be backed up. When
synchronized with the volume, the backup mirror is ready to be used as a
snapshot mirror. However, it continues being updated until it is detached
during the actual snapshot portion of the procedure. This may take some
time, depending on the volume size.
To create a snapshot mirror for a volume, use the following command:
# vxassist snapstart volume_name
For example. to create a snapshot mirror of a volume called voldef, use
the following command:
# vxassist snapstart voldef
Step 2. Choose a suitable time to create a snapshot volume.
If possible, plan to take the snapshot at a time when users are accessing
the volume as little as possible.
Step 3. Create a snapshot volume that reflects the original volume at the time of
the snapshot.
The online backup procedure is completed by running the vxassist
snapshot command on the volume with the snapshot mirror. This task
detaches the finished snapshot mirror, creates a new normal volume, and
attaches the snapshot mirror to it. The snapshot then becomes a
read-only volume. This step should only take a few minutes.