Veritas FlashSnap Point-In-Time Copy Solutions 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

24 Setting up volumes for instant snapshots
Preparing a volume for instant snapshot operations
3 If you are going to create a snapshot volume by breaking off existing plexes,
use the following command to add one or more snapshot mirrors to the
volume:
# vxsnap [-b] [-g diskgroup ] addmir volume [nmirror= N ] \
[alloc=
storage_attribute [,...]]
By default, one snapshot plex is added unless you specify a number using
the
nmirror attribute. For a backup, you should usually only require one
plex. The mirrors remain in the SNAPATT state until they are fully
synchronized. The
-b option can be used to perform the synchronization in
the background. Once synchronized, the mirrors are placed in the
SNAPDONE state.
For example, the following command adds 2 mirrors to the volume, vol1,
on disks mydg10 and mydg11:
# vxsnap -g mydg addmir vol1 nmirror=2 alloc=mydg10,mydg11
Note: Do not perform this step if you create a full-sized snapshot volume
using a suitably prepared empty volume (see “Creating a volume for use as a
full-sized instant snapshot” on page 27), or if you create space-optimized
snapshots that use a cache (see “Creating a shared cache object” on
page 28).
If the disks that contain volumes and their snapshots are to be moved into
different disk groups, you must ensure that the disks that contain their DCO
plexes can accompany them. You can use storage attributes to specify which
disks to use for the DCO plexes. (If you do not want to use dirty region logging
(DRL) with a volume, you can specify the same disks as those on which the
volume is configured, assuming that space is available on the disks). For
example, to add a DCO object and DCO volume with plexes on disk05 and
disk06, and a region size of 32KB, to the volume, myvol, use the following
command:
# vxsnap -g mydg prepare myvol ndcomirs=2 regionsize=32k \
alloc=disk05,disk06
If required, you can use the vxassist move command to relocate DCO plexes to
different disks. For example, the following command moves the plexes of the
DCO volume for volume vol1 from disk03 and disk04 to disk07 and
disk08:
# vxassist -g mydg move vol1_dcl !disk03 !disk04 disk07 \
disk08
To view the details of the DCO object and DCO volume that are associated with a
volume, use the
vxprint command. The following is example vxprint -vh