Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 5, Creating and Administering Subdisks
Associating Log Subdisks
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size that fits the hole in the sparse plex exactly. Then, associate the subdisk with the plex
by specifying the offset of the beginning of the hole in the plex, using the following
command:
# vxsd [-g diskgroup] -l offset assoc sparse_plex exact_size_subdisk
Note The subdisk must be exactly the right size. VxVM does not allow the space defined
for two subdisks to overlap within a plex.
For striped or RAID-5 plexes, use the following command to specify a column number
and column offset for the subdisk to be added:
# vxsd [-g diskgroup] -l column_#/offset assoc plex subdisk ...
If only one number is specified with the -l option for striped plexes, the number is
interpreted as a column number and the subdisk is associated at the end of the column.
Alternatively, to add M subdisks at the end of each of the N columns in a striped or
RAID-5 volume, you can use the following form of the vxsd command:
# vxsd [-g diskgroup] assoc plex subdisk1:0 ... subdiskM:N-1
The following example shows how to append three subdisk to the ends of the three
columns in a striped plex, vol-01, in the disk group, mydg:
# vxsd -g mydg assoc vol01-01 mydg10-01:0 mydg11-01:1 mydg12-01:2
If a subdisk is filling a “hole” in the plex (that is, some portion of the volume logical
address space is mapped by the subdisk), the subdisk is considered stale. If the volume is
enabled, the association operation regenerates data that belongs on the subdisk.
Otherwise, it is marked as stale and is recovered when the volume is started.
Associating Log Subdisks
Note The version 20 DCO volume layout includes space for a DRL. Do not apply the
procedure described in this section to a volume that has a version 20 DCO volume
associated with it. See “Preparing a Volume for DRL and Instant Snapshots” on
page 235 for more information.
Log subdisks are defined and added to a plex that is to become part of a volume on which
dirty region logging (DRL) is enabled. DRL is enabled for a volume when the volume is
mirrored and has at least one log subdisk.
For a description of DRL, see “Dirty Region Logging (DRL)” on page 42. Log subdisks are
ignored as far as the usual plex policies are concerned, and are only used to hold the dirty
region log.