VERITAS Volume Manager 3.5 User's Guide - VERITAS Enterprise Administrator (September 2004)

Volume Tasks
Using the Volume Snapshot Feature
Chapter 4 133
Using the Volume Snapshot Feature
The snapshot feature can be used to take a snapshot of a mirrored or an
unmirrored volume, but snapshot is not supported for RAID-5 volumes.
NOTE To take a snapshot of a volume, you must have an empty dynamic disk in
the volume’s disk group.
The snapshot feature enables quick and efficient online backup of
volumes, with minimum disruption to the user. Snapshot automatically
enables FastResync (FR) and creates a snapshot image of a volume,
which can be detached from the volume. The detached snapshot image
can be used for backup, or other purposes, while the original volume
remains in service. The snapshot can then be quickly reattached and
resynchronized with the volume, through the FR reconnection capability.
The snapshot volume can also be permanently disconnected from the
original volume.
You can attach more than one snapshot plex to a volume, by issuing
successive snapstart commands on the volume. This enables you to take
multiple snapshots of a single volume.
You can attach a snapshot to either the original volume or the snapshot
volume.
The following five snapshot commands are supported by VxVM, and are
accessed through the Volume context menu:
• Snap Start - “Creating a Snapshot Copy of a Volume” on page 134
Attaches the snapshot mirror to the original volume.
• Snap Shot - “Creating the New Volume” on page 135
Detaches the snapshot mirror from the original volume and creates a
snapshot volume that is associated with the snapshot mirror.
• Snap Back - “Merging a Snapshot Volume (Volume Snapback)” on
page 137
Reattaches the snapshot mirror to the original volume.