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

Chapter 9, Administering Volume Snapshots
Creating Instant Snapshots
285
The following example shows how to prepare a source volume set, vset1, and an
identical volume set, snapvset1, which is then used to create the snapshot:
# vxsnap -g mydg prepare vset1
# vxsnap -g mydg prepare snapvset1
# vxsnap -g mydg make source=vset1/snapvol=snapvset1
To create a full-sized third-mirror break-off snapshot, you must ensure that each volume
in the source volume set contains sufficient plexes. The following example shows how to
achieve this by using the vxsnap command to add the required number of plexes before
breaking off the snapshot:
# vxsnap -g mydg prepare vset2
# vxsnap -g mydg addmir vset2 nmirror=1
# vxsnap -g mydg make source=vset2/newvol=snapvset2/nmirror=1
See “Adding Snapshot Mirrors to a Volume” on page 285 for more information about
adding plexes to volumes or to volume sets.
To create a space-optimized instant snapshot of a volume set, the commands are again
identical to that for a standalone volume as shown in these examples:
# vxsnap -g mydg prepare vset3
# vxsnap -g mydg make source=vset3/newvol=snapvset3/cachesize=20m
# vxsnap -g mydg prepare vset4
# vxsnap -g mydg make source=vset4/newvol=snapvset4/cache=mycobj
Here a new cache object is created for the volume set, vset3, and an existing cache object,
mycobj, is used for vset4.
See “Creating and Administering Volume Sets” on page 311 for more information on
creating and administering volume sets.
Adding Snapshot Mirrors to a Volume
If you are going to create a full-sized break-off snapshot volume, you can use the
following command to add new snapshot mirrors to a volume:
# vxsnap [-b] [-g diskgroup] addmir volume|volume_set [nmirror=N] \
[alloc=storage_attributes]
Note The volume must have been prepared using the vxsnap prepare command as
described in “Preparing a Volume for DRL and Instant Snapshots” on page 235.
If a volume set name is specified instead of a volume, the specified number of
plexes is added to each volume in the volume set.