VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Enabling Persistent FastResync on Existing Volumes with Associated Snapshots
210 VERITAS Volume Manager Administrator’s Guide
Note The DCO plexes require persistent storage space on disk to be available for the
FastResync maps. To make room for the DCO plexes, you may need to add extra
disks to the disk group, or reconfigure existing volumes to free up space in the disk
group.Anotherway toadddisk spaceis tousethe disk groupmove featureto bring
in spare disks from a different disk group. For moreinformation, see “Reorganizing
the Contents of Disk Groups” on page 121.
Perform the following steps to enable Persistent FastResync on an existing volume that
has attached snapshot plexes or associated snapshot volumes:
1. Upgrade the disk group containing the existing volume to at least version 90 before
performing the remainder of the procedure described in this section. Use the
following command to check the version of a disk group:
# vxdg list diskgroup
To upgrade a disk group to the latest version, use the following command:
# vxdg upgrade diskgroup
For more information, see “Upgrading a Disk Group” on page 133.
2. For a volume that has one or more associated snapshot volumes, it is recommended
that you use following command to reattach and resynchronize each snapshot:
# vxassist [-g diskgroup] snapback snapvol
If Non-Persistent FastResync was enabled on the volume before the snapshot was
taken, the data in the snapshot plexes is quickly resynchronized from the original
volume. If Non-Persistent FastResync was not enabled, a full resynchronization is
performed.
If you choose to reattach all the snapshots, you need only add a DCO and DCO
volume to the original volume.
If you choose not to snapback the snapshot volumes, you must add a DCO and DCO
volume to the original volume, and separately to each of its snapshot volumes. This
approach requires a full resynchronization on the first subsequent snapback of each
snapshot volume after you have enabled Persistent FastResync.
3. Use the following command to turn off Non-Persistent FastResync on the original
volume if it is currently enabled:
# vxvol [-g diskgroup] set fastresync=off volume
If you are uncertain about which volumes have Non-Persistent FastResync enabled,
use the following command to obtain a listing of such volumes:
# vxprint [-g diskgroup] -F “%name” \
-e “v_fastresync=on && !v_hasdcolog”