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335Administering volume snapshots
Creating instant snapshots
VOLUME INDEX LENGTH KSTATE CONTEXT
svol_0 0 204800 ENABLED -
svol_1 1 409600 ENABLED -
svol_2 2 614400 ENABLED -
A full-sized instant snapshot of a volume set can be created using a prepared
volume set in which each volume is the same size as the corresponding volume
in the parent volume set. Alternatively, you can use the nmirrors attribute to
specify the number of plexes that are to be broken off provided that sufficient
plexes exist for each volume in the volume set.
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 336 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 361 for more information
on creating and administering volume sets.