Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

283Administering volumes
Enabling FastResync on a volume
such as backup and decision support. See “Administering volume snapshots” on page 295
and “FastResync” on page 66 for more information.
There are two possible versions of FastResync that can be enabled on a volume:
■ Persistent FastResync holds copies of the FastResync maps on disk. These can be
used for the speedy recovery of mirrored volumes if a system is rebooted. This form
of FastResync requires that either a version 0 or a version 20 data change object
(DCO) and DCO volume first be associated with the volume.
See “Adding a version 0 DCO and DCO volume” on page 348, and “Preparing a
volume for DRL and instant snapshots” on page 266 for more information on version
0 and version 20 DCO volumes respectively.
If the existing volume was created in a previous release of VxVM, and it has any
attached snapshot plexes or it is associated with any snapshot volumes, follow the
procedure given in “Upgrading existing volumes to use version 20 DCOs” on
page 270.
■ Non-Persistent FastResync holds the FastResync maps in memory. These do not
survive on a system that is rebooted.
By default, FastResync is not enabled on newly created volumes. Specify the
fastresync=on attribute to the vxassist make command if you want to enable
FastResync on a volume that you are creating.
Note: It is not possible to configure both Persistent and Non-Persistent FastResync on a
volume. Persistent FastResync is used if a DCO is associated with the volume. Otherwise,
Non-Persistent FastResync is used.
To turn FastResync on for an existing volume, specify
fastresync=on to the vxvol
command as shown here:
# vxvol [-g diskgroup] set fastresync=on volume
Note: To use FastResync with a snapshot, FastResync must be enabled before the
snapshot is taken, and must remain enabled until after the snapback is completed.
Checking whether FastResync is enabled on a volume
To check whether FastResync is enabled on a volume, use the following command:
# vxprint [-g diskgroup] -F%fastresync volume
This command returns on if FastResync is enabled; otherwise, it returns off.
If FastResync is enabled, to check whether it is Non-Persistent or Persistent FastResync,
use the following command:
# vxprint [-g diskgroup] -F%hasdcolog volume
This command returns on if Persistent FastResync is enabled; otherwise, it returns off.