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

Chapter 1, Recovery from Hardware Failure

Failures on RAID-5 Volumes

Forcibly Starting RAID-5 Volumes

You can start a volume even if subdisks are marked as stale: for example, if a stopped

volume has stale parity and no RAID-5 logs, and a disk becomes detached and then

reattached.

The subdisk is considered stale even though the data is not out of date (because the

volume was in use when the subdisk was unavailable) and the RAID-5 volume is

considered invalid. To prevent this case, always have multiple valid RAID-5 logs

associated with the array whenever possible.

To start a RAID-5 volume with stale subdisks, you can use the -f option with the vxvol

start command. This causes all stale subdisks to be marked as non-stale. Marking takes

place before the start operation evaluates the validity of the RAID-5 volume and what is

needed to start it. Also, you can mark individual subdisks as non-stale by using the

following command:

# vxmend [-g diskgroup] fix unstale subdisk

◆ If some subdisks are stale and need recovery, and if valid logs exist, the volume is

enabled by placing it in the ENABLED kernel state and the volume is available for use

during the subdisk recovery. Otherwise, the volume kernel state is set to DETACHED

and it is not available during subdisk recovery.

This is done because if the system were to crash or the volume was ungracefully

stopped while it was active, the parity becomes stale, making the volume unusable. If

this is undesirable, the volume can be started with the -o unsafe start option.

Caution The -o unsafe start option is considered dangerous, as it can make the

contents of the volume unusable. It is therefore not recommended.

◆ The volume state is set to RECOVER and stale subdisks are restored. As the data on

each subdisk becomes valid, the subdisk is marked as no longer stale.

If any subdisk recovery fails and there are no valid logs, the volume start is aborted

because the subdisk remains stale and a system crash makes the RAID-5 volume

unusable. This can also be overridden by using the -o unsafe start option.

Caution The -o unsafe start option is considered dangerous, as it can make the

contents of the volume unusable. It is therefore not recommended.

If the volume has valid logs, subdisk recovery failures are noted but they do not stop

the start procedure.

◆ When all subdisks have been recovered, the volume is placed in the ENABLED kernel

state and marked as ACTIVE. It is now started.