VERITAS Volume Manager 3.5 Troubleshooting Guide (August 2002)

Failures on RAID-5 Volumes
12 VERITAS Volume Manager Troubleshooting Guide
Recovery After Moving RAID-5 Subdisks
When RAID-5 subdisks are moved and replaced, the new subdisks are marked as STALE
in anticipation of recovery. If the volume is active, the vxsd command may be used to
recover the volume. If the volume is not active, it is recovered when it is next started. The
RAID-5 volume is degraded for the duration of the recovery operation.
Any failure in the stripes involved in the move makes the volume unusable. The RAID-5
volume can also become invalid if its parity becomes stale. To avoid this occurring, vxsd
does not allow a subdisk move in the following situations:
◆ a stale subdisk occupies any of the same stripes as the subdisk being moved
◆ the RAID-5 volume is stopped but was not shut down cleanly; that is, the parity is
considered stale
◆ the RAID-5 volume is active and has no valid log areas
Only the third case can be overridden by using the -o force option.
Subdisks of RAID-5 volumes can also be split and joined by using the vxsd split
command and the vxsd join command. These operations work the same way as those
for mirrored volumes.
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