VERITAS Volume Manager 4.1 Troubleshooting Guide

Recovery from Hardware Failure
Failures on RAID-5 Volumes
Chapter 1 25
Log Plex Recovery
RAID-5 log plexes can become detached due to disk failures. These RAID-5 logs can be
reattached by using the att keyword for the vxplex command. To reattach the failed RAID-5
log plex, use the following command:
# vxplex att r5vol r5vol-l1
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 27, 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 vxvolrecover 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.