Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

■ Run vxassist snapstart to create a snapshot mirror.
■ Run vxassist snapshot to create a snapshot volume.
The vxassist snapstart step creates a write-only backup plex which gets attached
to and synchronized with the volume. When synchronized with the volume, the
backup plex is ready to be used as a snapshot mirror. The end of the update
procedure is indicated by the new snapshot mirror changing its state to
SNAPDONE. This change can be tracked by the vxassist snapwait task, which
waits until at least one of the mirrors changes its state to SNAPDONE. If the attach
process fails, the snapshot mirror is removed and its space is released.
Note: If the snapstart procedure is interrupted, the snapshot mirror is
automatically removed when the volume is started.
Once the snapshot mirror is synchronized, it continues being updated until it is
detached. You can then select a convenient time at which to create a snapshot
volume as an image of the existing volume. You can also ask users to refrain from
using the system during the brief time required to perform the snapshot (typically
less than a minute). The amount of time involved in creating the snapshot mirror
is long in contrast to the brief amount of time that it takes to create the snapshot
volume.
The online backup procedure is completed by running the vxassist snapshot
command on a volume with a SNAPDONE mirror. This task detaches the finished
snapshot (which becomes a normal mirror), creates a new normal volume and
attaches the snapshot mirror to the snapshot volume. The snapshot then becomes
a normal, functioning volume and the state of the snapshot is set to ACTIVE.
245Administering volume snapshots
Creating traditional third-mirror break-off snapshots