Veritas Storage Foundation Intelligent Storage Provisioning 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

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If you intend to take a space-optimized instant snapshot of the volume, you
must first set up a shared cache volume in the same disk group as the volume.
This cache object for this cache volume can be maintained by using the
vxcache command.
For full-sized instant snapshots, linked break-off snapshots and
space-optimized instant snapshots, you must also create a volume for use as
the snapshot volume. This volume must have the same region size as that of
the volume for which the snapshot is being created. In addition, a volume
that is created for use as a full-sized instant snapshot must be the same size
as the volume for which the snapshot is being created.
See “Creating a shared cache volume and preparing space-optimized
snapshots” on page 101.
See “Creating a volume for use as a full-sized instant or linked break-off
snapshot” on page 100.
If you intend to split the clone pool that contains snapshots into separate
disk groups (for example, to perform off-host processing), the clone pool must
only contain fully synchronized full-sized instant snapshots (which do not
require a cache volume). You cannot split off a clone pool that contains either
a cache volume or space-optimized instant snapshots.
Creating and managing space-optimized instant snapshots
Space-optimized instant snapshots are not suitable for write-intensive volumes
(such as for database redo logs) because the copy-on-write mechanism may degrade
the performance of the volume.
If you intend to split the volume and snapshot into separate disk groups (for
example, to perform off-host processing), you must use a fully synchronized linked
break-off snapshot (which does not require a cache object). You cannot use a
space-optimized instant snapshot for this purpose.
Creation of space-optimized snapshots that use a shared cache fails if the region
size specified for the volume is smaller than the region size set on the cache.
If the region size of a space-optimized snapshot differs from the region size of
the cache, this can degrade the system’s performance compared to the case where
the region sizes are the same.
For space-optimized instant snapshots that share a cache object, the specified
region size must be greater than or equal to the region size specified for the cache
object.
See “Creating a shared cache volume and preparing space-optimized snapshots”
on page 101.
Administering instant snapshots
Creating instant snapshots
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