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

80 Administering application volumes
Preparing a volume for DRL and snapshot operations
Preparing a volume for DRL and snapshot
operations
To prepare an application volume for dirty region logging (DRL) and instant
snapshot operations, a data change object (DCO) and DCO volume must be
associated with the volume.
Note: The procedure in this section describes how to add a version 20 DCO and
DCO volume to an application volume that you previously created in a disk
group with a version number of 110 or greater. If you are creating a new volume
in a disk group with a version number of 110 or greater, you can specify the co-
creation of a DCO and DCO volume and enabling of DRL.
See “Creating a volume for use with snapshots and DRL” on page 73.
See “Adding logs to a volume” on page 86.
You may need an additional license to use the DRL and FastResync features.
Use the following command to add a version 20 DCO and DCO volume to an
existing volume:
# vxassist [-g diskgroup] [-P storage_pool ] addlog volume \
[nlog=
number ] logtype=dco [regionsize= size ] \
[drl=yes|no|sequential]
The nlog attribute specifies the number of DCO plexes that are created in the
DCO volume. It is recommended that you configure as many DCO plexes as there
are data plexes in the volume. For example, specify nlog=3 for a volume with 3
data plexes.
The value of the regionsize attribute specifies the size of the tracked regions
in the volume. A write to a region is tracked by setting a bit in the change map.
The default value is 64k (64KB). A smaller value requires more disk space for the
change maps, but the finer granularity provides faster resynchronization.
To enable DRL logging on the volume, specify
drl=yes. If sequential DRL is
required, specify
drl=sequential.
You can also specify
vxassist-style storage attributes to define the disks that
can and/or cannot be used for the plexes of the DCO volume.