VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Chapter 9, Administering Hot-Relocation
How Hot-Relocation works
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3. If no spare disks are available or additional space is needed, vxrelocd uses free
space on disks in the same disk group, except those disks that have been excluded for
hot-relocation use (marked nohotuse). When vxrelocd has relocated the subdisks,
it reattaches each relocated subdisk to its plex.
4. Finally, vxrelocd initiates appropriate recovery procedures. For example, recovery
includes mirror resynchronization for mirrored volumes or data recovery for RAID-5
volumes. It also notifies the system administrator of the hot-relocation and recovery
actions that have been taken.
If relocation is not possible, vxrelocd notifies the system administrator and takes no
further action.
Note Hot-relocation doesnot guarantee the same layout of dataor the same performance
after relocation. The system administrator can make configuration changes after
hot-relocation occurs.
Relocation of failing subdisks is not possible in the following cases:
◆ The failing subdisks are on non-redundant volumes (that is, volumes of types other
than mirrored or RAID-5).
◆ If you use vxdiskadm to remove a disk that contains subdisks of a volume.
◆ There are insufficient spare disks or free disk space in the disk group.
◆ The only available space is on a disk that already contains a mirror of the failing plex.
◆ The only available space is on a disk that already contains the RAID-5 log plex or one
of its healthy subdisks, failing subdisks in the RAID-5 plex cannot be relocated.
◆ If a mirrored volume has a dirty region logging (DRL) log subdisk as part of its data
plex, failing subdisks belonging to that plex cannot be relocated.
◆ If a RAID-5 volume log plex or a mirrored volume DRL log plex fails, a new log plex
is created elsewhere. There is no need to relocate the failed subdisks of log plex.
See the xvrelocd(1M) manual page for more information about the hot-relocation
daemon.
“Example of Hot-Relocation for a Subdisk in a RAID-5 Volume” on page 230 illustrates
the hot-relocation process inthe case of thefailure of asingle subdisk of a RAID-5volume.