You can only have one RAID-5 plex per RAID-5 volume. Additional plexes become RAID-5 log plexes, which log information about data and parity being written to the volume. When you create a RAID-5 volume using the vxassist command, a log plex is created for that volume by default.
To add a RAID-5 log to an existing volume, use the following command:
# vxassist [-b] [-g diskgroup] addlog volume [loglen=length]
If you specify the -b option, adding the new log is a background task.
When you add the first log to a volume, you can specify the log length. Any logs that you add subsequently are configured with the same length as the existing log.
For example, to create a log for the RAID-5 volume volraid, in the disk group mydg, use the following command:
# vxassist -g mydg addlog volraid