VERITAS Volume Manager 3.5 Troubleshooting Guide (September 2004)

Recovery from Hardware Failure

Failures on RAID-5 Volumes

Chapter 1

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: 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 17 for details).

Forcibly Starting RAID-5 Volumes

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The subdisk is considered stale even though the data is not out of date (because the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.

To start a RAID-5 volume with stale subdisks, you can use the -f option with the vxvol

start command. This causes all stale subdisks to be marked as non-stale. Marking

takes place before the start operation evaluates the validity of the RAID-5 volume and

what is needed to start it. Also, you can mark individual subdisks as non-stale by using

the following command:

# vxmend fix unstale

subdisk

• If some subdisks are stale and need recovery, and if valid logs exist, the volume is

enabled by placing it in the ENABLED kernel state and the volume is available for use

during the subdisk recovery. Otherwise, the volume kernel state is set to DETACHED

and it is not available during subdisk recovery.