Veritas Storage Foundation Intelligent Storage Provisioning 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

96 Administering instant snapshots
Creating a volume for use as a full-sized instant or linked break-off snapshot
Creating a volume for use as a full-sized instant or
linked break-off snapshot
If you want to create a full-sized instant or linked break-off snapshot for an
original volume, you can use an empty volume with the required capability, and
with the same length and region size as the original volume.
To create an empty volume for use by a full-sized instant or linked break-off
snapshot
1 Use the
vxprint command on the original volume to find the required size
for the snapshot volume.
# LEN=‘vxprint [-g diskgroup ] -F%len volume ‘
Note: The command shown in this and subsequent steps assumes that you
are using a Bourne-type shell such as
sh, ksh or bash. You may need to
modify the command for other shells such as csh or tcsh.
2 Use the
vxassist command to create a volume, snapvol, of the required size
and redundancy:
# vxassist [-g diskgroup ] [-P storage_pool ] make snapvol \
$LEN [
storage_specification ...] [ attribute ...] \
type=snapshot [regionsize=size] init=active
The attribute regionsize specifies the minimum size of each chunk (or
region) of a volume whose contents are tracked for changes. The region size
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).
Note: 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.
The init=active attribute is specified to make the volume available
immediately.
The following example creates a 10-gigabyte mirrored volume, ttsnpvol,
in the clone storage pool, ttclpool:
# vxassist -g ttdg -P ttclpool make ttsnpvol 10g \
capability=’DataMirroring(nmirs=2)’ type=snapshot \
init=active