Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Enabling FastResync on a volume
The recommended method for enabling FastResync on a volume with a version
20 DCO is to use the vxsnap prepare command.
See “Preparing a volume for DRL and instant snapshots” on page 359.
Note: To use this feature, you need a FastResync license.
FastResync quickly and efficiently resynchronizes stale mirrors. When you use
FastResync with operations such as backup and decision support, it also increases
the efficiency of the VxVM snapshot mechanism.
See “FastResync” on page 63.
You can enable the following versions of FastResync on a volume:
■ Persistent FastResync holds copies of the FastResync maps on disk. If a system
is rebooted, you can use these copies to quickly recover mirrored volumes. To
use this form of FastResync, you must first associate a version 0 or a version
20 data change object (DCO) and DCO volume with the volume.
See “Upgrading existing volumes to use version 20 DCOs” on page 366.
See “Preparing a volume for DRL and instant snapshots” on page 359.
■ Non-Persistent FastResync holds the FastResync maps in memory. These maps
do not survive on a system that is rebooted.
By default, FastResync is not enabled on newly-created volumes. If you want to
enable FastResync on a volume that you create, specify the fastresync=on
attribute to the vxassist make command.
Note: You cannot configure Persistent and Non-Persistent FastResync on a volume.
If a DCO is associated with the volume, Persistent FastResync is used. Otherwise,
Non-Persistent FastResync is used.
To turn on FastResync for an existing volume, specify fastresync=on to the vxvol
command as follows:
# vxvol [-g diskgroup] set fastresync=on volume
To use FastResync with a snapshot, you must enable FastResync before the
snapshot is taken, and it must remain enabled until after the snapback is
completed.
373Administering volumes
Enabling FastResync on a volume