Veritas Storage Foundation Intelligent Storage Provisioning 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008
98 Administering instant snapshots
Creating a shared cache volume and preparing space-optimized snapshots
must be a power of 2, and be greater than or equal to 16KB. A smaller value
requires more disk space for the change maps, but the finer granularity
provides faster resynchronization. The default region size is 64k (64KB).
The following example creates a 1GB mirrored cache volume, cachevol, in
the clone storage pool, myclpool, within the disk group, mydg:
# vxassist -g mydg -P myclpool make mycache 1g \
rules="mirror 2" type=cachevolume
3 Once the cache volume has been created, use the following command to
prepare each space-optimized snapshot that uses the cache volume:
# vxassist [-g
diskgroup
] [-P
storage_pool
] make
sovol
\
srcvol_len
[
storage_specification
...] [
attribute
...] \
type=snapshot cachevolume=
cachevol
init=active
Note: The srcvol_len argument specifies the length of the source volume for
which the snapshot is being prepared. This value defines the logical size of
the snapshot. The actual amount of storage that the snapshot requires is
less than this, and is limited by the size of the cache volume.
For example, this command creates a space-optimized snapshot volume
that uses the cache volume, mycache:
# vxassist -g mydg -P myclpool make mysovol 10g \
type=snapshot cachevolume=mycache
Note: The argument 10g is the size of the source volume for which the
snapshot mysovol is being prepared.
Once created, such a volume is ready for use to take a space-optimized
instant snapshot.
Alternatively, you can use the following command to create a cache volume and
prepare the space-optimized snapshot volumes in a single operation:
# vxassist -M make <<!!
volumegroup {
diskgroup "
diskgroup
"
volume "
cachevol
"
cache_size
{
type cachevolume
[
storage_specification
]
[regionsize
size
]
}
volume "
sovol1
"
vol1_size
{
init active
cachevolume "
cachevol
"
}
volume "
sovol2
"
vol2_size
{
init active
cachevolume "
cachevol
"
}
.