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

314 Administering volume snapshots
Creating instant snapshots
Creating a volume for use as a full-sized instant or linked break-off
snapshot
To create an empty volume for use by a full-sized instant snapshot or a linked break-
off snapshot
1Use the vxprint command on the original volume to find the required size for the
snapshot volume.
# LEN=‘vxprint [-g diskgroup] -F%len volume‘
Note: The command shown in this and subsequent steps assumes that you are using a
Bourne-type shell such as
sh, ksh or bash. You may need to modify the command
for other shells such as csh or tcsh.
2Use the
vxprint command on the original volume to discover the name of its DCO:
# DCONAME=‘vxprint [-g diskgroup] -F%dco_name volume‘
3Use the vxprint command on the DCO to discover its region size (in blocks):
# RSZ=‘vxprint [-g diskgroup] -F%regionsz $DCONAME‘
4Use the vxassist command to create a volume, snapvol, of the required size and
redundancy, together with a version 20 DCO volume with the correct region size:
# vxassist [-g diskgroup] make snapvol $LEN \
[layout=mirror nmirror=number] logtype=dco drl=off \
dcoversion=20 [ndcomirror=number] regionsz=$RSZ \
init=active [storage_attributes]
Specify the same number of DCO mirrors (ndcomirror) as the number of mirrors
in the volume (nmirror). The init=active attribute is used to make the volume
available immediately. You can use storage attributes to specify which disks should
be used for the volume.
As an alternative to creating the snapshot volume and its DCO volume in a single
step, you can first create the volume, and then prepare it for instant snapshot
operations as shown here:
# vxassist [-g diskgroup] make snapvol $LEN \
[layout=mirror nmirror=number] init=active \
[storage_attributes]
# vxsnap [-g diskgroup] prepare snapvol [ndcomirs=number] \
regionsize=$RSZ [storage_attributes]