VERITAS Volume Manager 4.1 Troubleshooting Guide

Recovery from Hardware Failure
Failures on RAID-5 Volumes
Chapter 126
NOTE RAID-5 subdisk moves are performed in the same way as subdisk moves for
other volume types, but without the penalty of degraded redundancy.
Starting RAID-5 Volumes
When a RAID-5 volume is started, it can be in one of many states. After a normal system
shutdown, the volume should be clean and require no recovery. However, if the volume was
not closed, or was not unmounted before a crash, it can require recovery when it is started,
before it can be made available. This section describes actions that can be taken under certain
conditions.
Under normal conditions, volumes are started automatically after a reboot and any recovery
takes place automatically or is done through the vxrecover command.
Unstartable RAID-5 Volumes
A RAID-5 volume is unusable if some part of the RAID-5 plex does not map the volume
length:
• the RAID-5 plex cannot be sparse in relation to the RAID-5 volume length
• the RAID-5 plex does not map a region where two subdisks have failed within a stripe,
either because they are stale or because they are built on a failed disk
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 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. The situation shown in Figure 1-3, “Invalid RAID-5
Volume,” illustrates a RAID-5 volume that has become invalid due to stale parity and a failed
subdisk.