Veritas FlashSnap Point-In-Time Copy Solutions 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

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 zoo (the TUTIL0 and PUTIL0 columns are omitted for

clarity):

TTY NAME ASSOC KSTATE LENGTH PLOFFS STATE

...

v zoo fsgen ENABLED 1024 - ACTIVE

pl zoo-01 zoo ENABLED 1024 - ACTIVE

sd disk01-01 zoo-01 ENABLED 1024 0 -

pl foo-02 zoo ENABLED 1024 - ACTIVE

sd disk02-01 zoo-02 ENABLED 1024 0 -

dc zoo_dco zoo - - - -

v zoo_dcl gen ENABLED 132 - ACTIVE

pl zoo_dcl-01 zoo_dcl ENABLED 132 - ACTIVE

sd disk03-01 zoo_dcl-01 ENABLED 132 0 -

pl zoo_dcl-02 zoo_dcl ENABLED 132 - ACTIVE

sd disk 04-01 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.

See “Considerations for placing DCO plexes” on page 32.

For more information on DCO objects, see the vxassist(1M) and vxsnap(1M)

manual pages.

Considerations for placing DCO plexes

If you use the vxassist command or the Veritas Enterprise Administrator (VEA)

to create both a volume and its DCO, or the vxsnap prepare command to add a

DCO to a volume, the DCO plexes are automatically placed on different disks from

the data plexes of the parent volume. In previous releases, version 0 DCO plexes

were placed on the same disks as the data plexes for convenience when performing

disk group split and move operations. As the version 20 DCOs in VxVM 4.0 and

later releases support dirty region logging (DRL) in addition to persistent

FastResync, it is preferable for the DCO plexes to be separated from the data

plexes. This improves the I/O performance of the volume, and provides resilience

for the DRL logs.

If you use the vxsnap prepare command to set up a DCO, you must ensure that

the disks that contain the plexes of the DCO volume accompany their parent

volume during the move. Use the vxprint command on a volume to examine the

configuration of its associated DCO volume.

Setting up volumes for instant snapshots

Preparing a volume for instant snapshot operations