Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Note: You cannot use the vxvol set len command to increase the size of a volume
unless the needed space is available in the volume's plexes. When you reduce the
volume's size using the vxvol set len command, the freed space is not released
into the disk group’s free space pool.
If a volume is active and you reduce its length, you must force the operation using
the -o force option to vxvol. This precaution ensures that space is not removed
accidentally from applications using the volume.
You can change the length of logs using the following command:
# vxvol [-g diskgroup] set loglen=length log_volume
Warning: Sparse log plexes are not valid. They must map the entire length of the
log. If increasing the log length makes any of the logs invalid, the operation is not
allowed. Also, if the volume is not active and is dirty (for example, if it has not
been shut down cleanly), you cannot change the log length. If you are decreasing
the log length, this feature avoids losing any of the log contents. If you are
increasing the log length, it avoids introducing random data into the logs.
Adding a mirror to a volume
You can add a mirror to a volume with the vxassist command, as follows:
# vxassist [-b] [-g diskgroup] mirror volume
Specifying the -b option makes synchronizing the new mirror a background task.
For example, to create a mirror of the volume voltest in the disk group, mydg,
use the following command:
# vxassist -b -g mydg mirror voltest
You can also mirror a volume by creating a plex and then attaching it to a volume
using the following commands:
# vxmake [-g diskgroup] plex plex sd=subdisk ...
# vxplex [-g diskgroup] att volume plex
Mirroring all volumes
To mirror all volumes in a disk group to available disk space, use the following
command:
355Administering volumes
Adding a mirror to a volume