Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 11, Configuring Off-Host Processing
Implementing Off-Host Processing Solutions
319
Note If the volume was created under VxVM 4.0 or a later release, and it is not
associated with a new-style DCO object and DCO volume, follow the procedure
described in “Preparing a Volume for DRL and Instant Snapshots” on page 235.
If the volume was created before release 4.0 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 240.
2. Use the following command on the primary host to check whether FastResync is
enabled on the volume:
# vxprint -g volumedg -F%fastresync volume
This command returns on if FastResync is enabled; otherwise, it returns off.
If FastResync is disabled, enable it using the following command on the primary host:
# vxvol -g volumedg set fastresync=on volume
3. Add one or more snapshot plexes to the volume using this command:
# vxsnap -g volumedg addmir volume [nmirror=N]
By default, one snapshot plex is added unless you specify a number using the
nmirror attribute. For a backup, you should usually only require one plex.
Alternatively, create a new volume for use as the snapshot volume as described in
“Creating a Volume for Use as a Full-Sized Instant Snapshot” on page 293.
4. If you added one of more snapshot plexes to the volume in step 3, create a full-sized
instant snapshot volume, snapvol, by running the following command on the primary
host:
# vxsnap -g volumedg make source=volume/newvol=snapvol/nmirror=N
This version of the vxsnap make command uses the nmirror attribute to specify
how many snapshot plexes of the original volume are to be broken off to form the
snapshot volume.
If you created a new volume, snapvol, for use as the snapshot volume in step 3, use the
following version of the vxsnap command to create the snapshot on this volume:
# vxsnap -g volumedg make source=volume/snapvol=snapvol
Note By default, VxVM attempts to avoid placing 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