Veritas Volume Manager 5.0.1 Troubleshooting Guide, HP-UX 11i v3, First Edition, November 2009

Figure 1-3
Invalid RAID-5 volume
disk00-00 disk01-00 disk02-00
disk03-00 disk04-00 disk05-00
RAID-5 plex
W
X
Y
Z
W
X
Y
Z
Data
Data
Data
Data
Data
Data
Data
Data
Parity
Parity
Parity
Parity
There are four stripes in the RAID-5 array. All parity is stale and subdisk disk05-00
has failed. This makes stripes X and Y unusable because two failures have occurred
within those stripes.
This qualifies as two failures within a stripe and prevents the use of the volume.
In this case, the output display from the vxvol start command is as follows:
VxVM vxvol ERROR V-5-1-1237 Volume r5vol is not startable;
some subdisks are unusable and the parity is stale.
This situation can be avoided by always using two or more RAID-5 log plexes in
RAID-5 volumes. RAID-5 log plexes prevent the parity within the volume from
becoming stale which prevents this situation.
See “System failures” on page 18.
Forcibly starting a RAID-5 volume with stale subdisks
You can start a volume even if subdisks are marked as stale: for example, if a
stopped volume has stale parity and no RAID-5 logs, and a disk becomes detached
and then reattached.
The subdisk is considered stale even though the data is not out of date (because
the volume was in use when the subdisk was unavailable) and the RAID-5 volume
is considered invalid. To prevent this case, always have multiple valid RAID-5
logs associated with the array whenever possible.
Recovering from hardware failure
Failures on RAID-5 volumes
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