250Creating volumesCreating a volume with a version 0 DCO volume

#vxassist [-b] [-g diskgroup] make volume length \ layout=concat-mirror [nmirror=number]

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 252. This is the preferred and recommended method.

See “Determining the DCO version number” on page 277 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 356.

Note: You need a Veritas FlashSnapTM 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

1Ensure that the disk group has been upgraded to version 90. Use the following command to check the version of a disk group: