VERITAS Volume Manager 3.5 Troubleshooting Guide (August 2002)

Chapter 1, Recovery from Hardware Failure

Failures on RAID-5 Volumes

When this occurs, the vxvol start command returns the following error message:

vxvm:vxvol: ERROR: Volume r5vol is not startable; RAID-5 plex does

not map entire volume length.

At this point, the contents of the RAID-5 volume are unusable.

Another possible waythat aRAID-5 volume canbecome unstartable isifthe parityis 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. The situation shown in “Invalid RAID-5

Volume” illustrates a RAID-5 volume that has become invalid due to stale parity and a

failed subdisk.

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 6 for details).

disk00-00 disk01-00 disk02-00

disk03-00 disk04-00 disk05-00

RAID-5 Plex

Data

Parity