Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

If a disk fails completely, VxVM can detach the disk from its disk group. All plexes
on the disk are disabled. If there are any unmirrored volumes on a disk when it
is detached, those volumes are also disabled.
Apparent disk failure may not be due to a fault in the physical disk media or the
disk controller, but may instead be caused by a fault in an intermediate or ancillary
component such as a cable, host bus adapter, or power supply.
The hot-relocation feature in VxVM automatically detects disk failures, and notifies
the system administrator and other nominated users of the failures by electronic
mail. Hot-relocation also attempts to use spare disks and free disk space to restore
redundancy and to preserve access to mirrored and RAID-5 volumes.
See “How hot-relocation works” on page 406.
If hot-relocation is disabled or you miss the electronic mail, you can use the
vxprint command or the graphical user interface to examine the status of the
disks. You may also see driver error messages on the console or in the system
messages file.
Failed disks must be removed and replaced manually.
See “Removing and replacing disks” on page 130.
For more information about recovering volumes and their data after hardware
failure, see the Veritas Volume Manager Troubleshooting Guide.
How hot-relocation works
Hot-relocation allows a system to react automatically to I/O failures on redundant
(mirrored or RAID-5) VxVM objects, and to restore redundancy and access to those
objects. VxVM detects I/O failures on objects and relocates the affected subdisks
to disks designated as spare disks or to free space within the disk group. VxVM
then reconstructs the objects that existed before the failure and makes them
redundant and accessible again.
When a partial disk failure occurs (that is, a failure affecting only some subdisks
on a disk), redundant data on the failed portion of the disk is relocated. Existing
volumes on the unaffected portions of the disk remain accessible.
Hot-relocation is 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.
Hot-relocation is enabled by default and takes effect without the intervention of
the system administrator when a failure occurs.
The hot-relocation daemon, vxrelocd, detects and reacts to VxVM events that
signify the following types of failures:
Administering hot-relocation
How hot-relocation works
406