334Administering 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