Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

To back up a volume using the vxassist command

Create a snapshot mirror for a volume using the following command:

# vxassist [-b] [-g diskgroup] snapstart [nmirror=N] volume

For example, to create a snapshot mirror of a volume called voldef, use the

following command:

# vxassist [-g diskgroup] snapstart voldef

The vxassist snapstart task creates a write-only mirror, which is attached

to and synchronized from the volume to be backed up.

By default, VxVM attempts to avoid placing snapshot mirrors on a disk that

already holds any plexes of a data volume. However, this may be impossible

if insufficient space is available in the disk group. In this case, VxVM uses

any available space on other disks in the disk group. If the snapshot plexes

are placed on disks which are used to hold the plexes of other volumes, this

may cause problems when you subsequently attempt to move a snapshot

volume into another disk group.

See “Moving DCO volumes between disk groups” on page 232.

To override the default storage allocation policy, you can use storage attributes

to specify explicitly which disks to use for the snapshot plexes.

See “Creating a volume on specific disks” on page 283.

If you start vxassist snapstart in the background using the -b option, you

can use the vxassist snapwait command to wait for the creation of the

mirror to complete as shown here:

# vxassist [-g diskgroup] snapwait volume

If vxassist snapstart is not run in the background, it does not exit until

the mirror has been synchronized with the volume. The mirror is then ready

to be used as a plex of a snapshot volume. While attached to the original

volume, its contents continue to be updated until you take the snapshot.

Use the nmirror attribute to create as many snapshot mirrors as you need

for the snapshot volume. For a backup, you should usually only require the

default of one.

It is also possible to make a snapshot plex from an existing plex in a volume.

See “Converting a plex into a snapshot plex” on page 400.

Choose a suitable time to create a snapshot. If possible, plan to take the

snapshot at a time when users are accessing the volume as little as possible.

Administering volume snapshots

Creating traditional third-mirror break-off snapshots

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