Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Preparing a Volume for DRL and Instant Snapshots
236 VERITAS Volume Manager Administrator’s Guide
You can also specify vxassist-style storage attributes to define the disks that can and/or
cannot be used for the plexes of the DCO volume. See “Specifying Storage for Version 20
DCO Plexes” on page 236 for details.
Note 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
Vol ume with a RA ID- 5 Volu me” on page 237 for details.
By default, a version 20 DCO volume contains 32 per-volume maps. If you require
more maps than this, you can use the vxsnap addmap command to add more
maps. See the vxsnap(1M) manual page for details of this command.
Specifying Storage for Version 20 DCO Plexes
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 mirrored DCO volume with plexes
on disk05 and disk06 to the volume, myvol, use the following command:
# vxsnap -g mydg prepare myvol ndcomirs=2 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-01ENABLED 132 0 -
pl vol1_dcl-02 vol1_dcl ENABLED 132 - ACTIVE
sd disk04-01 vol1_dcl-02ENABLED 132 0 -