Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

268 Administering volumes
Preparing a volume for DRL and instant snapshots
sd disk01-01 vol1-01 ENABLED 1024 0 -
pl foo-02 vol1 ENABLED 1024 - ACTIVE
sd disk02-01 vol1-02 ENABLED 1024 0 -
dc vol1_dco vol1 - - - -
v vol1_dcl gen ENABLED 132 - ACTIVE
pl vol1_dcl-01 vol1_dcl ENABLED 132 - ACTIVE
sd disk03-01 vol1_dcl-01 ENABLED 132 0 -
pl vol1_dcl-02 vol1_dcl ENABLED 132 - ACTIVE
sd disk04-01 vol1_dcl-02 ENABLED 132 0 -
In this output, the DCO object is shown as vol1_dco, and the DCO volume as
vol1_dcl with 2 plexes, vol1_dcl-01 and vol1_dcl-02.
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,
vol1_dcl, for volume vol1 from disk03 and disk04 to disk07 and disk08:
# vxassist -g mydg move vol1_dcl !disk03 !disk04 disk07 disk08
For more information, see “Moving DCO volumes between disk groups” on page 192, and
the
vxassist(1M) and vxsnap(1M) manual pages.
Using a DCO and DCO volume with a RAID-5 volume
The procedure in the previous section can be used to add a DCO and DCO volume to a
RAID-5 volume. This allows you to use Persistent FastResync on the volume for fast
resynchronization of snapshots on returning them to their original volume. However, the
procedure has the side effect of converting the RAID-5 volume into a special type of
layered volume. You can create space-optimized instant snapshots of such a volume, and
you can add mirrors that may be broken off as full-sized instant snapshots. You cannot
relayout or resize such a volume unless you convert it back to a pure RAID-5 volume.
To convert a volume back to a RAID-5 volume, remove any snapshot plexes from the
volume, and dissociate the DCO and DCO volume from the layered volume using the
procedure described in “Removing support for DRL and instant snapshots from a volume”
on page 270. You can then perform relayout and resize operations on the resulting non-
layered RAID-5 volume.
To allow Persistent FastResync to be used with the RAID-5 volume again, re-associate the
DCO and DCO volume as described in “Preparing a volume for DRL and instant
snapshots” on page 266.
Note: Dissociating a DCO and DCO volume disables FastResync on the volume. A full
resynchronization of any remaining snapshots is required when they are snapped back.