VERITAS Volume Manager 3.5 User's Guide - VERITAS Enterprise Administrator (September 2004)

Disk Tasks
Commands for Hot Relocation
Chapter 3 81
Commands for Hot Relocation
The Hot Spare and Hot Relocation procedures enable a system to
automatically react to I/O failures on redundant (mirrored or RAID-5)
volumes, and to restore redundancy and access to those volumes. The
following commands can be used to perform relocation tasks:
• “Undoing Hot Relocation” on page 83
• “Clearing Relocation Information for Dynamic Disk Groups” on
page 84
• “Customizing Disks for Hot Relocation” on page 85
NOTE The Hot Relocation and Hot Spare operations are only performed for
redundant (mirrored or RAID-5) subdisks on a failed disk.
Non-redundant subdisks on a failed disk are not relocated, but the
system administrator is notified of their failure.
About Hot Spare and Hot Relocation
One or more disks in each dynamic disk group can be designated as hot
spares by using the “set disk usage” command. These hot spare disks
provide a location where data can be moved from failed disks or volumes.
In Hot Spare mode, all subdisks containing redundant volumes will be
moved together from a failed disk to a spare disk. In order for the Hot
Spare operation to occur, there must be enough free space on the spare
disk for all the redundant volumes from the original disk.
When a disk fails, hot relocation automatically moves all subdisks
containing redundant volumes from the failed disk to hot spare disks. If
no disks have been designated as spares or there is not enough spare
disk space, a combination of spare space and free space is used.
Depending on available disk space, the subdisks are not always all
moved to the same disk, but may be scattered within the dynamic disk
group.