VERITAS Volume Manager 3.1 Administrator's Guide

Recovery

RAID-5 Recovery

Chapter 8374

regeneration must be kept across reboots. Otherwise, the process has to

start all over again.

To avoid the restart process, parity regeneration is checkpointed. This

means that the offset up to which the parity has been regenerated is

saved in the conﬁguration database. The -o checkpt=

size

option

controls how often the checkpoint is saved. If the option is not speciﬁed,

the default checkpoint size is used.

Because saving the checkpoint offset requires a transaction, making the

checkpoint size too small can extend the time required to regenerate

parity. After a system reboot, a RAID-5 volume that has a checkpoint

offset smaller than the volume length starts a parity resynchronization

at the checkpoint offset.

Subdisk Recovery

Stale subdisk recovery is usually done at volume start time. However,

the process doing the recovery can crash, or the can volume start with an

option to prevent subdisk recovery. In addition, the disk on which the

subdisk resides can be replaced without recovery operations being

performed. In any case, a subdisk recovery can be done by using the

recover keyword of the vxvol command. For example, to recover the

stale subdisk in the RAID-5 volume shown in Figure 8-1, Invalid RAID-5

Volume,, use the following command:

# vxvol recover r5vol disk01-00

A RAID-5 volume that has multiple stale subdisks can be caught up all

at once. To catch multiple stale subdisks, use the vxvol recover

command with only the volume name, as follows:

# vxvol recover r5vol

Recovering Logs After Failures

RAID-5 log plexes can become detached due to disk failures, as shown in

Figure 8-2, Read-Modify-Write,. These RAID-5 logs can be reattached by

using the att keyword for the vxplex command. To reattach the failed

RAID-5 log plex, use this command:

# vxplex att r5vol r5vol-l1