VERITAS Volume Manager 3.5 Troubleshooting Guide (August 2002)

Failures on RAID-5 Volumes
10 VERITAS Volume Manager Troubleshooting Guide
Note Following severe hardware failure of several disks or other related subsystems
underlying a RAID-5 plex, it may be impossible to recover the volume using the
methods described in this chapter. In this case, remove the volume, recreate it on
hardwarethat isfunctioning correctly,and restorethe contents ofthe volume froma
backup.
Parity Resynchronization
In most cases, a RAID-5 array does not have stale parity. Stale parity only occurs after all
RAID-5 log plexes for the RAID-5 volume have failed, and then only if there is a system
failure. Even if a RAID-5 volume has stale parity, it is usually repaired as part of the
volume start process.
If a volume without valid RAID-5 logs is started and the process is killed before the
volume is resynchronized, the result is an active volume with stale parity. For an example
of the outputof thevxprint -ht command, see thefollowing example forastale RAID-5
volume:
V NAME RVG KSTATE STATE LENGTH READPOL PREFPLEX UTYPE
PL NAME VOLUME KSTATE STATE LENGTH LAYOUT NCOL/WID MODE
SD NAME PLEX DISK DISKOFFSLENGTH [COL/]OFF DEVICE MODE
SV NAME PLEX VOLNAME NVOLLAYRLENGTH [COL/]OFF AM/NM MODE
...
v r5vol - ENABLED NEEDSYNC204800 RAID - raid5
pl r5vol-01 r5vol ENABLED ACTIVE 204800 RAID 3/16 RW
sd disk01-01 r5vol-01disk01 0 102400 0/0 c2t9d0 ENA
sd disk02-01 r5vol-01disk02 0 102400 1/0 c2t10d0 dS
sd disk03-01 r5vol-01disk03 0 102400 2/0 c2t11d0 ENA
...
This output lists the volume state as NEEDSYNC, indicating that the parity needs to be
resynchronized. The state could also have been SYNC, indicating that a synchronization
was attempted at start time and that a synchronization process should be doing the
synchronization. If no such process exists or if the volume is in the NEEDSYNC state, a
synchronization can be manually started by using the resync keyword for the vxvol
command. For example, to resynchronize the RAID-5 volume in the figure “Invalid
RAID-5 Volume” on page 13, use the following command:
# vxvol resync r5vol