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250 Creating volumes
Creating 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 FlashSnap
TM
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: