Veritas Volume Manager 5.0.1 Troubleshooting Guide, HP-UX 11i v3, First Edition, November 2009

Parity resynchronization and stale subdisk recovery are typically performed when

the RAID-5 volume is started, or shortly after the system boots. They can also be

performed by running the vxrecover command.

See “Unstartable RAID-5 volumes” on page 25.

If hot-relocation is enabled at the time of a disk failure, system administrator

intervention is not required unless no suitable disk space is available for relocation.

Hot-relocation is triggered by the failure and the system administrator is notified

of the failure by electronic mail.

Hot relocation automatically attempts to relocate the subdisks of a failing RAID-5

plex. After any relocation takes place, the hot-relocation daemon (vxrelocd) also

initiates a parity resynchronization.

In the case of a failing RAID-5 log plex, relocation occurs only if the log plex is

mirrored; the vxrelocd daemon then initiates a mirror resynchronization to

recreate the RAID-5 log plex. If hot-relocation is disabled at the time of a failure,

the system administrator may need to initiate a resynchronization or recovery.

Note: Following severe hardware failure of several disks or other related

subsystems underlying a RAID-5 plex, it may be only be possible to recover the

volume by removing the volume, recreating it on hardware that is functioning

correctly, and restoring the contents of the volume from a backup.

Resynchronizing parity on a RAID-5 volume

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.

The following example is output from the vxprint -ht command for a stale

RAID-5 volume:

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 NEEDSYNC 204800 RAID - raid5

pl r5vol-01 r5vol ENABLED ACTIVE 204800 RAID 3/16 RW

sd disk01-01 r5vol-01 disk01 0 102400 0/0 c2t9d0 ENA

Recovering from hardware failure

Failures on RAID-5 volumes