Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

241Creating volumes

Creating a volume with a version 0 DCO volume

If a data change object (DCO) and DCO volume are associated with a volume, this allows

Persistent FastResync to be used with the volume. (See “How persistent FastResync

works with snapshots” on page 70 for details of how Persistent FastResync performs fast

resynchronization of snapshot mirrors when they are returned to their original volume.)

Note: The procedure described in this section creates a volume with a data change object

(DCO) and DCO volume that has a version 0 layout as introduced in VxVM 3.2. The

version 0 layout supports traditional (third-mirror) snapshots, but not full-sized instant

snapshots, space-optimized instant snapshots nor DRL configured within the DCO

volume. See “Version 0 DCO volume layout” on page 69 and “Version 20 DCO volume

layout” on page 69 for a description of the differences between the old and new DCO

volume layouts.

For details of how to configure a volume with a version 20 DCO and DCO volume, see

“Creating a volume with a version 20 DCO volume” on page 242. This is the preferred

and recommended method.

See “Determining the DCO version number” on page 269 for details of how to determine

the version number of a volume’s DCO.

To perform fast resynchronization of mirrors after a system crash or reboot, you must also

enable dirty region logging (DRL) on a mirrored volume. To add a DCO object and DCO

volume to a volume on which DRL logging is enabled, follow the procedure described in

“Adding a version 0 DCO and DCO volume” on page 348.

Note: You need a Veritas FlashSnap

or FastResync license to use the Persistent

FastResync feature. Even if you do not have a license, you can configure a DCO object

and DCO volume so that snap objects are associated with the original and snapshot

volumes. For more information about snap objects, see “How persistent FastResync works

with snapshots” on page 70.

To create a volume with an attached version 0 DCO object and volume

1 Ensure that the disk group has been upgraded to version 90. Use the following

command to check the version of a disk group:

# vxdg list diskgroup

To upgrade a disk group to version 90, use the following command:

# vxdg -T 90 upgrade diskgroup

For more information, see “Upgrading a disk group” on page 200.