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334 Administering volume snapshots
Creating instant snapshots
In this example, snapvol1 is a full-sized snapshot that uses a prepared volume,
snapvol2 is a space-optimized snapshot that uses a prepared cache, and
snapvol3 is a break-off full-sized snapshot that is formed from plexes of the
original volume.
An example of where you might want to create mixed types of snapshots at the
same time is when taking snapshots of volumes containing database redo logs
and database tables:
# vxsnap -g mydg make \
source=logv1/newvol=snplogv1/drl=sequential/nmirror=1 \
source=logv2/newvol=snplogv2/drl=sequential/nmirror=1 \
source=datav1/newvol=snpdatav1/cache=mydgcobj/drl=on \
source=datav2/newvol=snpdatav2/cache=mydgcobj/drl=on
In this example, sequential DRL is enabled for the snapshots of the redo log
volumes, and normal DRL is applied to the snapshots of the volumes that
contain the database tables. The two space-optimized snapshots are configured
to share the same cache object in the disk group. Also note that break-off
snapshots are used for the redo logs as such volumes are write intensive.
Creating instant snapshots of volume sets
Volume set names can be used in place of volume names with the following
vxsnap operations on instant snapshots: addmir, dis, make, prepare, reattach,
refresh, restore, rmmir, split, syncpause, syncresume, syncstart, syncstop,
syncwait, and unprepare.
The procedure for creating an instant snapshot of a volume set is the same as
that for a standalone volume. However, there are certain restrictions if a full-
sized instant snapshot is to be created from a prepared volume set. A full-sized
instant 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