Veritas Volume Manager 5.0 Troubleshooting Guide, HP-UX 11i v3, First Edition, May 2008

22 Recovery from hardware failure

Failures on RAID-5 volumes

Another possible way that a RAID-5 volume can become unstartable is if the

parity is stale and a subdisk becomes detached or stale. This occurs because

within the stripes that contain the failed subdisk, the parity stripe unit is invalid

(because the parity is stale) and the stripe unit on the bad subdisk is also invalid.

Figure 1-3 illustrates a RAID-5 volume that has become invalid due to stale

parity and a failed subdisk.

Figure 1-3 Invalid RAID-5 volume

This example shows 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 15

for details).

disk00-00 disk01-00 disk02-00

disk03-00 disk04-00 disk05-00

RAID-5 plex

Data

Parity