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

space-optimized snapshots that use a shared cache fails if the region size of the
volume is smaller than the region size of 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.
If you need to create several space-optimized instant snapshots for the volumes
in a disk group, you may find it more convenient to create a single shared cache
volume in the disk group rather than a separate cache volume for each snapshot.
Creating a cache volume and preparing the space-optimized volumes
Use the following procedure to create a shared cache volume and prepare
space-optimized snapshots.
To create a shared cache volume and prepare any space-optimized snapshots
1
Decide on the following characteristics that you want to allocate to the cache
volume:
■ The size of the cache volume should be sufficient to record changes to the
parent volumes during the interval between snapshot refreshes. A
suggested value is 10% of the total size of the parent volumes for a refresh
interval of 24 hours.
■ If redundancy is a desired characteristic of the cache volume, it should
be mirrored. This increases the space required by the cache volume in
proportion to the number of mirrors that it has.
■ If the cache volume is mirrored, space is required on at least as many disks
as it has mirrors. These disks should not be shared with the disks used
for the parent volumes. The disks should also be chosen to avoid impacting
Administering instant snapshots
Creating a shared cache volume and preparing space-optimized snapshots
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