VERITAS Volume Manager 3.1 Administrator's Guide

Volume Tasks
Associating Subdisks
Chapter 6 283
a size that fits the hole in the sparse plex exactly. Then, to associate the
subdisk with the plex by specifying the offset of the beginning of the hole
in the plex, use the following command:
# vxsd -l offset assoc sparse_plex_name
exact_size_subdisk
NOTE The subdisk must be exactly the right size because Volume Manager
does not allow for the space defined by two subdisks to overlap within a
single plex.
For striped subdisks, to specify a column number and column offset for
the subdisk, use the following command:
# vxsd -l column_ #/ offset assoc plex_name sd_name ...
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.
Associating Log Subdisks
Log subdisks are defined for and added to a plex that is to become part
of a volume using Dirty Region Logging. Dirty Region Logging is enabled
for a volume when the volume is mirrored and has at least one log
subdisk.
For a description of Dirty Region Logging, see “Dirty Region Logging”,
and “Dirty Region Logging and Cluster Environments”. Log subdisks are
ignored as far as the usual plex policies are concerned, and are only used
to hold the dirty region log.
NOTE Only one log subdisk can be associated with a plex. Because this log
subdisk is frequently written, care should be taken to position it on a
disk that is not heavily used. Placing a log subdisk on a heavily-used disk
can degrade system performance.
To add a log subdisk to an existing plex, use the following command:
# vxsd aslog plex subdisk