Veritas Volume Manager 5.0 Troubleshooting Guide Guide (September 2006)

23Recovery from hardware failure
Failures on RAID-5 volumes
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 V-5-1-1236 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. Figure 1-3 illustrates a RAID-5 volume
that has become invalid due to stale parity and a failed subdisk.