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

Chapter 8, Administering Volumes

Preparing a Volume for DRL and Instant Snapshots

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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 161,

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

Vol um e” on page 239. 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 235.

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.