VERITAS Volume Manager 4.1 Administrator's Guide

Configuring Off-Host Processing
Implementing Off-Host Processing Solutions
Chapter 11 391
# vxprint -g volumedg -F%hasdcolog volume
This command returns on if there is a DCO and DCO volume; otherwise,
it returns off.
If the volume is not associated with a DCO object and DCO volume,
follow the procedure described in “Adding a DCO and DCO Volume” on
page 277.
Step 2. Use the following command on the primary host to check whether
FastResync is enabled on a volume:
# vxprint -g volumedg -F%fastresync volume
This command returns on if FastResync is enabled; otherwise, it returns
off.
If Persistent FastResync is disabled, enable it using the following
command on the master host:
# vxvol -g volumedg set fastresync=on volume
Step 3. If the volume does not already contain a snapshot plex, create one using
the following command on the primary host:
# vxassist -g volumedg [-b] snapstart [nmirror=N] volume
The vxassist snapstart task creates a write-only mirror, which is
attached to and synchronized from the volume to be backed up.
NOTE By default, VxVM attempts to avoid placing a snapshot mirrors on a disk
that already holds any plexes of a data volume. However, this may be
impossible if insufficient space is available in the disk group. In this case,
VxVM uses any available space on other disks in the disk group. If the
snapshot plexes are placed on disks which are used to hold the plexes of
other volumes, this may cause problems when you subsequently attempt
to move a snapshot volume into another disk group as described in
“Considerations for Placing DCO Plexes” on page 177. To override the
default storage allocation policy, you can use storage attributes to specify
explicitly which disks to use for the snapshot plexes. See “Creating a
Volume on Specific Disks” on page 236 for more information.