Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

See “Specifying storage for version 20 DCO plexes” on page 360.
The vxsnap prepare command automatically enables Persistent FastResync on
the volume. Persistent FastResync is also set automatically on any snapshots that
are generated from a volume on which this feature is enabled.
If the volume is a RAID-5 volume, it is converted to a layered volume that can be
used with instant snapshots and Persistent FastResync.
See “Using a DCO and DCO volume with a RAID-5 volume” on page 361.
By default, a version 20 DCO volume contains 32 per-volume maps. If you require
more maps, you can use the vxsnap addmap command to add them.
See the vxsnap(1M) manual page.
Specifying storage for version 20 DCO plexes
If you move the disks that contain volumes and their snapshots 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 mirrored DCO volume with plexes on disk05 and disk06 to the volume, myvol,
use the following command:
# vxsnap -g mydg prepare myvol ndcomirs=2 alloc=disk05,disk06
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 output
for the volume named vol1 (the TUTIL0 and PUTIL0 columns are omitted for
clarity):
TY NAME ASSOC KSTATE LENGTH PLOFFS STATE ...
v vol1 fsgen ENABLED 1024 - ACTIVE
pl vol1-01 vol1 ENABLED 1024 - ACTIVE
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 -
Administering volumes
Preparing a volume for DRL and instant snapshots
360