VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
FastResync
Chapter 158
volume is the name of the volume being snapshotted. This default can be
overridden by using the option -o name=pattern, as described on the
vxassist(1M) manual page.
To snapshot all the volumes in a single disk group, specify the option -o
allvols to vxassist. However, this fails if any of the volumes in the disk
group do not have a complete snapshot plex.
It is also possible to take several snapshots of the same volume. A new
FastResync change map is produced for each snapshot taken to minimize
the resynchronization time for each snapshot.
By default, the snapshot plex is resynchronized from the data in the
original volume during a snapback operation. Alternatively, you can
choose the snapshot plex as the preferred copy of the data when
performing a snapback as illustrated in Figure 1-35, “Resynchronizing
the Original Volume from the Snapshot,” Specifying the option -o
resyncfromreplica to vxassist resynchronizes the original volume from
the data in the snapshot.
Figure 1-35 Resynchronizing the Original Volume from the Snapshot
NOTE The original volume must not be in use during a snapback operation that
specifies the option -o resyncfromreplica to resynchronize the volume
from a snapshot. Stop any application, such as a database, and unmount
any file systems that are configured to use the volume.
It is possible to grow the replica volume, or the original volume, and still
use FastResync. Growing the volume extends the map that FastResync
uses to track changes to the original volume. This can change either the
size of the map, or the size of the region represented by each bit in the
map. In either case, the part of the map that corresponds to the grown
Original
volume
snapshot
Snapshot
volume
Snapshot
mirror
-o resyncfromreplica snapback
Refresh on
snapback