VERITAS Storage Foundation 4.1 Intelligent Storage Provisioning Administrator's Guide

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Administering Instant Snapshots
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VERITAS Volume Manager (VxVM) provides the capability for taking an image of a volume at a
given point in time. Such an image is referred to as a volume snapshot.
Instant volume snapshots allow you to make backup copies of your volumes online with minimal
interruption to users. You can then use the backup copies to restore data that has been lost due to
disk failure, software errors or human mistakes, or to create replica volumes for the purposes of
report generation, application development, or testing.
Two kinds of instant volume snapshots are supported for use with application volumes created by
VERITAS Intelligent Storage Provisioning (ISP):
◆ Full-sized instant snapshots require an empty volume to be prepared for use as the snapshot
volume as described in “Creating a Volume for Use as a Full-Sized Instant Snapshot” on
page 76. The length of this volume must be the same as that of the volume whose snapshot is
being taken. A snapshot volume can be created in either a data pool or in a clone pool. It must
be created in a clone pool if you want to move it to a separate disk group. See “Preparing
Storage Pools for Full-Sized Instant Snapshots” on page 75 for details.
◆ Space-optimized instant snapshots require less space than a full-sized instant snapshot but they
cannot be dissociated from their original volume nor can they be moved into a different disk
group. A space-optimized snapshot uses a storage pool or cache, which can be shared by one or
more other space-optimized snapshots. You must set up the cache and the space-optimized
snapshot volume in advance of creating any space-optimized snapshots, as described in
“Creating a Shared Cache Volume and Preparing Space-Optimized Snapshots” on page 77.
The creation and administration of instant snapshots is described in “Creating Instant Snapshots”
on page 81 and in subsequent sections. For details of how to use volume snapshots to implement
off-host online backup, see “Implementing Off-Host Processing Solutions” on page 94.