Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

snapshot of a volume set must itself be a volume set with the same number of
volumes, and the same volume sizes and index numbers as the parent. For example,
if a volume set contains three volumes with sizes 1GB, 2GB and 3GB, and indexes
0, 1 and 2 respectively, then the snapshot volume set must have three volumes
with the same sizes matched to the same set of index numbers. The corresponding
volumes in the parent and snapshot volume sets are also subject to the same
restrictions as apply between standalone volumes and their snapshots.
You can use the vxvset list command to verify that the volume sets have
identical characteristics as shown in this example:
# vxvset -g mydg list vset1
VOLUME INDEX LENGTH KSTATE CONTEXT
vol_0 0 204800 ENABLED -
vol_1 1 409600 ENABLED -
vol_2 2 614400 ENABLED -
# vxvset -g mydg list snapvset1
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
Administering volume snapshots
Creating instant snapshots
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