Veritas Storage Foundation Intelligent Storage Provisioning 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

Creating a volume for use with snapshots and DRL
If the dirty region logging (DRL) or instant snapshot features are going to be used
with an application volume, a version 20 data change object (DCO) and DCO volume
must be associated with the volume.
If you want to create a volume of which you can take instant snapshots, the
InstantSnapshottable capability or template must be specified (unless this
capability is already implied by another capability or template), as shown in the
following command:
# vxassist -g mydg -P mypool make mir3vol 1g \
capability=’DataMirroring(nmirs=3),InstantSnapshottable’ \
init=active
By default, a data change object (DCO) and DCO volume with a single plex are
associated with a volume to enable the instant snapshot capability. To increase
the redundancy of the DCO volume, specify the DCOLogMirroring capability as
shown in the following command:
# vxassist -g mydg -P mypool make mir3vol 1g \
capability=’DataMirroring(nmirs=3),InstantSnapshottable,\
DCOLogMirroring(nlogs=3)’ init=active
In this example, the same degree of redundancy is created for the DCO volume as
for the data volume.
The DCO and DCO volume that are added by the InstantSnapShottable capability
also provide the dirty region logging (DRL) capability that speeds recovery of
mirrored volumes after a system crash. To enable DRL, specify either the attribute
drl=on for full DRL, or drl=sequential for sequential DRL (used with volumes
containing database replay logs). By default, DRL is disabled (drl=off).
For example, the following command enables DRL for the volume, mir3vol, that
is being created:
# vxassist -g mydg -P mypool make mir3vol 1g \
capability=’DataMirroring(nmirs=3),InstantSnapshottable’ \
drl=on init=active
Traditional DRL logs are implemented using a dedicated plex for each log copy,
rather than using a DCO volume, and are supported for mirrored volume layouts
only.
See “Adding logs to a volume” on page 89.
75Creating application volumes
Creating a volume for use with snapshots and DRL