Veritas Volume Manager 4.1 Troubleshooting Guide (HP-UX 11i v3, February 2007)

Chapter 1, Recovery from Hardware Failure

Failures on RAID-5 Volumes

A disk containing a RAID-5 log plex can also fail. The failure of a single RAID-5 log plex

has no direct effect on the operation of a volume provided that the RAID-5 log is mirrored.

However, loss of all RAID-5 log plexes in a volume makes it vulnerable to a complete

failure. In the output of the vxprint -ht command, failure within a RAID-5 log plex is

indicated by the plex state being shown as BADLOG rather than LOG. This is shown in the

following display, where the RAID-5 log plex r5vol-02 has failed:

V NAME RVG/VSET/COKSTATESTATE 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 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 DISABLEDBADLOG 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.