VERITAS Volume Manager 3.1 Administrator's Guide

Volume Tasks
Performing Online Backup
Chapter 6 289
FastResync (Fast Mirror Resynchronization)
NOTE You may need an additional license to use this feature.
The FastResync feature (also called Fast Mirror Resynchronization,
which is abbreviated as FMR) performs quick and efficient
resynchronization of stale mirrors by increasing the efficiency of the
VxVM snapshot mechanism to better support operations such as backup
and decision support.
Enabling FMR
When a new volume is created with vxassist, an attribute can be
specified to turn FMR on or off. Both keywords fmr and fastresync can
be used as attributes to specify that FMR will be used (or not) on a
volume.
To create a volume with FMR enabled, use the vxassist make command
as follows:
# vxassist make volume_name size fmr=on
The default is for FMR to be off, but you can change the default in the
vxassist default file.
The FMR functionality can also be turned ON or OFF with the vxvol
command. To use FMR, FMR must be enabled when the snapshot is
taken, and FMR must remain enabled until after the snapback is
completed.Turning FMR off will free all of the tracking maps for the
specified volume. All subsequent reattaches will not use the FMR facility,
but do a full resynchronization of the volume. This occurs even if FMR is
later turned on.
To turn FMR on, use the following command:
# vxvol set fmr=on volume_name
To turn FMR off, use the following command:
# vxvol set fmr=off volume_name
Merging a Snapshot Volume
A snapshot copy of a volume can be merged back with the original
volume. The snapshot plex is detached from the snapshot volume and