Veritas FlashSnap Point-In-Time Copy Solutions 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008
27Setting up volumes for instant snapshots
Creating a volume for use as a full-sized instant snapshot
Creating a volume for use as a full-sized instant
snapshot
If you want to create a full-sized instant snapshot for an original volume that
does not contain any spare plexes, you can use an empty volume with the
required degree of redundancy, and with the same size and same region size as
the original volume.
To create an empty volume for use by a full-sized instant 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
vxprint command on the original volume to discover the name of
its DCO:
# DCONAME=‘vxprint [-g
diskgroup
] -F%dco_name
volume
‘
3 Use the vxprint command on the DCO to discover its region size (in blocks):
# RSZ=‘vxprint [-g
diskgroup
] -F%regionsz $DCONAME‘
4 Use the vxassist command to create a volume, snapvol, of the required size
and redundancy, together with a version 20 DCO volume with the correct
region size:
# vxassist [-g
diskgroup
] make
snapvol
$LEN \
[layout=mirror nmirror=
number
] logtype=dco drl=no \
dcoversion=20 [ndcomirror=
number
] regionsz=$RSZ \
init=active [
storage_attributes
]
It is recommended that you specify the same number of DCO mirrors
(ndcomirror) as the number of mirrors in the volume (nmirror). The
init=active attribute is used to make the volume available immediately.
You can use storage attributes to specify which disks should be used for the
volume.
As an alternative to creating the snapshot volume and its DCO volume in a
single step, you can first create the volume, and then prepare it for instant
snapshot operations as shown here:
# vxassist [-g
diskgroup
] make
snapvol
$LEN \
[layout=mirror nmirror=
number
] init=active \
[
storage_attributes
]
# vxsnap [-g
diskgroup
] prepare
snapvol
[ndcomirs=
number
] \
regionsize=$RSZ [
storage_attributes
]