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

325Administering volume snapshots
Creating instant snapshots
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 325 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 those 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 353 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 267.
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.
By default, the
vxsnap addmir command adds one snapshot mirror to a volume unless
you use the nmirror attribute to specify a different number of mirrors. The mirrors
remain in the SNAPATT state until they are fully synchronized. The
-b option can be used
to perform the synchronization in the background. Once synchronized, the mirrors are
placed in the SNAPDONE state.
For example, the following command adds 2 mirrors to the volume, vol1, on disks
mydg10 and mydg11:
# vxsnap -g mydg addmir vol1 nmirror=2 alloc=mydg10,mydg11