VERITAS Storage Foundation 4.1 Intelligent Storage Provisioning Administrator's Guide

Chapter 5, Administering Instant Snapshots

Implementing Off-Host Processing Solutions

These applications use the Persistent FastResync and disk group move, split and join features of

VxVM in conjunction with full-sized instant volume snapshots. It is assumed that you have

configured a data storage pool containing the application volumes, and a clone storage pool

containing prepared empty volumes for any snapshots. You must also have associated a data

change object (DCO) and DCO volume with all these volumes.

Implementing Off-Host Online Backup

This section describes a procedure for implementing off-host online backup for a volume in a

private disk group. The intention is to present an outline of how to set up a regular backup cycle by

combining the Persistent FastResync and disk group split and join features of VxVM. It is beyond

the scope of this guide to describe how to configure a database to use this procedure, or how to

perform the backup itself.

To back up a volume in a private disk group, use the following procedure.

1. Create a full-sized instant snapshot volume, snapvol, using the following command on the

primary host:

# vxsnap -g volumedg make source=volume/snapvol=snapvol

This command uses the specified prepared snapshot volume, snapvol, to form the snapshot

volume. (See “Creating a Volume for Use as a Full-Sized Instant Snapshot” on page 76 for

details.)

If a database spans more than one volume, you can specify all the volumes and their snapshot

volumes using one command, as shown in this example:

# vxsnap -g dbasedg make source=vol1/snapvol=snapvol1 \

source=vol2/snapvol=snapvol2 \

source=vol3/snapvol=snapvol3

Note This step sets up the snapshot volumes ready for the backup cycle, and starts tracking

changes to the original volumes. When you are ready to make a backup, proceed to

step 2.

2. On the primary host, suspend updates to the volume that contains the database tables. The

database may have a hot backup mode that allows you to do this by temporarily suspending

writes to its tables.

3. On the primary host, refresh the plexes of the snapshot volume using the following command:

# vxsnap [-g diskgroup] refresh snapvol source=volume sync=yes

For a database, multiple snapshots can be refreshed in parallel, as shown in this example:

# vxsnap -g dbasedg refresh snapvol1 source=vol1 snapvol2 \

source=vol2 snapvol3 source=vol3 sync=yes