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

Chapter 7, Creating Volumes
Creating a RAID-5 Volume
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Creating a RAID-5 Volume
Note VxVM supports this feature for private disk groups, but not for shareable disk
groups in a cluster environment.
Note You need a full license to use this feature.
You can create RAID-5 volumes by using either the vxassist command (recommended)
or the vxmake command. Both approaches are described below.
Note A RAID-5 volume requires space to be available on at least as many disks in the disk
group as the number of columns in the volume. Additional disks may be required
for any RAID-5 logs that are created.
A RAID-5 volume contains a RAID-5 data plex that consists of three or more subdisks
located on three or more physical disks. Only one RAID-5 data plex can exist per volume.
A RAID-5 volume can also contain one or more RAID-5 log plexes, which are used to log
information about data and parity being written to the volume. For more information on
RAID-5 volumes, see “RAID-5 (Striping with Parity)” on page 29.
Caution Do not create a RAID-5 volume with more than 8 columns because the volume
will be unrecoverable in the event of the failure of more than one disk.
To create a RAID-5 volume, use the following command:
# vxassist [-b] [-g diskgroup] make volume length layout=raid5 \
[ncol=number_of_columns] [stripewidth=size] [nlog=number] \
[loglen=log_length]
For example, to create the RAID-5 volume volraid together with 2 RAID-5 logs in the
disk group, mydg, use the following command:
# vxassist -b -g mydg make volraid 10g layout=raid5 nlog=2
This creates a RAID-5 volume with the default stripe unit size on the default number of
disks. It also creates two RAID-5 logs rather than the default of one log.
Note If you require RAID-5 logs, you must use the logdisk attribute to specify the disks
to be used for the log plexes.
RAID-5 logs can be concatenated or striped plexes, and each RAID-5 log associated with a
RAID-5 volume has a complete copy of the logging information for the volume. To
support concurrent access to the RAID-5 array, the log should be several times the stripe
size of the RAID-5 plex.