Veritas Volume Manager 5.0 Troubleshooting Guide Guide (September 2006)

22 Recovery from hardware failure
Failures on RAID-5 volumes
Stale subdisk recovery
Stale subdisk recovery is usually done at volume start time. However, the process doing
the recovery can crash, or the volume may be started with an option such as
-o
delayrecover that prevents subdisk recovery. In addition, the disk on which the subdisk
resides can be replaced without recovery operations being performed. In such cases, you
can perform subdisk recovery using the
vxvol recover command. For example, to
recover the stale subdisk in the RAID-5 volume shown in the figure “Invalid RAID-5
volume” on page 24, use the following command:
# vxvol -g mydg recover r5vol disk05-00
A RAID-5 volume that has multiple stale subdisks can be recovered in one operation. To
recover multiple stale subdisks, use the
vxvol recover command on the volume, as
follows:
# vxvol -g mydg recover r5vol
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.