Veritas Storage Foundation Intelligent Storage Provisioning 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

73Creating application volumes
Creating a volume for use with snapshots and DRL
}
};
This creates three volumes named mirvol1, mirvol2 and mirvol3. If volumes
with the same name prefix and numeric suffix already exist, the numbering of
the new volumes continues from the highest number found plus 1.
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):
# 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 here:
# 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
Note: 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 86.