VERITAS Volume Manager 4.1 Administrator's Guide

Administering Volumes
Adding a DCO and DCO Volume
Chapter 8 279
pl zoo_dcl-02 zoo_dcl ENABLED 132 - ACTIVE
sd c1t67d0-01 zoo_dcl-02 ENABLED 132 0 -
In this output, the DCO object is shown as zoo_dco, and the DCO volume
as zoo_dcl with 2 plexes, zoo_dcl-01 and zoo_dcl-02.
For more information, see the vxassist(1M) manual page.
Attaching a DCO and DCO volume to 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 enable Persistent
FastResync on the volume for fast resynchronization of snapshots on
snapback (see “Enabling FastResync on a Volume” on page 298).
However, the procedure has the side effect of converting the RAID-5
volume into a special type of layered volume. You cannot relayout or
resize such a volume unless you convert it back to a pure RAID-5 volume.
To do this, remove any snapshot plexes from the volume, and dissociate
the DCO and DCO volume from the layered volume using the procedure
described in “Removing a DCO and DCO Volume” on page 281. 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
“Reattaching a DCO and DCO Volume” on page 282.
NOTE Dissociating a DCO and DCO volume disables Persistent FastResync on
the volume. A full resynchronization of any remaining snapshots is
required when they are snapped back.
Specifying Storage for DCO Plexes
If the disks that contain volumes and their snapshots are to be moved or
split into different disk groups, the disks that contain their respective
DCO plexes must be able to accompany them. By default, VxVM
attempts to place the DCO plexes on the same disks as the data plexes of
the parent volume. However, this may be impossible if there is
insufficient space available on those disks. In this case, VxVM uses any
available space on other disks in the disk group. If the DCO plexes are