Veritas Volume Manager 5.0 Troubleshooting Guide, HP-UX 11i v3, First Edition, May 2008

17Recovery from hardware failure
Failures on RAID-5 volumes
V NAME RVG/VSET/COKSTATE STATE LENGTH READPOL PREFPLEX UTYPE
PL NAME VOLUME KSTATE STATE LENGTH LAYOUT NCOL/WID MODE
SD NAME PLEX DISK DISKOFFS LENGTH [COL/]OFF DEVICE MODE
SV NAME PLEX VOLNAME NVOLLAYR LENGTH [COL/]OFF AM/NM MODE
...
v r5vol - ENABLED ACTIVE 204800 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 ENA
sd disk03-01 r5vol-01disk03 0 102400 2/0 c2t11d0 ENA
pl r5vol-02 r5vol DISABLED BADLOG 1440 CONCAT - RW
sd disk04-01 r5vol-02disk04 0 1440 0 c2t12d0 ENA
pl r5vol-03 r5vol ENABLED LOG 1440 CONCAT - RW
sd disk05-01 r5vol-12disk05 0 1440 0 c2t14d0 ENA
Default startup recovery process for RAID-5
VxVM may need to perform several operations to restore fully the contents of a
RAID-5 volume and make it usable. Whenever a volume is started, any RAID-5
log plexes are zeroed before the volume is started. This prevents random data
from being interpreted as a log entry and corrupting the volume contents. Also,
some subdisks may need to be recovered, or the parity may need to be
resynchronized (if RAID-5 logs have failed).
VxVM takes the following steps when a RAID-5 volume is started:
1 If the RAID-5 volume was not cleanly shut down, it is checked for valid
RAID-5 log plexes.
■ If valid log plexes exist, they are replayed. This is done by placing the
volume in the DETACHED volume kernel state and setting the volume
state to REPLAY, and enabling the RAID-5 log plexes. If the logs can be
successfully read and the replay is successful, go to step 2.
■ If no valid logs exist, the parity must be resynchronized.
Resynchronization is done by placing the volume in the DETACHED
volume kernel state and setting the volume state to SYNC. Any log
plexes are left in the DISABLED plex kernel state.
The volume is not made available while the parity is resynchronized
because any subdisk failures during this period makes the volume
unusable. This can be overridden by using the -o unsafe start option
with the
vxvol command. If any stale subdisks exist, the RAID-5
volume is unusable.
Caution: The -o unsafe start option is considered dangerous, as it can
make the contents of the volume unusable. Using it is not recommended.