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

Chapter 9, Administering Hot-Relocation
Configuring a System for Hot-Relocation
233
When selecting space for relocation, hot-relocation preserves the redundancy
characteristics of the VxVM object to which the relocated subdisk belongs. For example,
hot-relocation ensures that subdisks from a failed plex are not relocated to a disk
containing a mirror of the failed plex. If redundancy cannot be preserved using any
available spare disks and/or free space, hot-relocation does not take place. If relocation is
not possible, the system administrator is notified and no further action is taken.
From the eligible disks, hot-relocation attempts to use the disk that is “closest” to the
failed disk. Thevalue of“closeness” dependson thecontroller, target, anddisk numberof
the failed disk. A disk on the same controller as the failed disk is closer than a disk on a
different controller. A disk under the same target as the failed disk is closer than one on a
different target.
Hot-relocation tries to move all subdisks from a failing drive to the same destination disk,
if possible.
When hot-relocation takes place, the failed subdisk is removed from the configuration
database, andVxVM ensures that the disk spaceused bythe failed subdisk is not recycled
as free space.
Configuring a System for Hot-Relocation
By designating spare disks and making free space on disks available for use by hot
relocation,you can controlhow disk space isused for relocating subdisksin the event of a
disk failure. If the combined free space and space on spare disks is not sufficient or does
not meet the redundancy constraints, the subdisks are not relocated.
◆ To find out which disks are spares or are excluded from hot-relocation, see
“Displaying Spare Disk Information” on page 234.
You can prepare for hot-relocation by designating one or more disks per disk group as
hot-relocation spares.
◆ To designate a disk as being a hot-relocation spare for a disk group, see “Marking a
Disk as a Hot-Relocation Spare” on page 234.
◆ To remove a disk from use as a hot-relocation spare, see “Removing a Disk from Use
as a Hot-Relocation Spare” on page 235.
If no spares are available at the time of a failure or if there is not enough space on the
spares, free space on disks in the same disk group as where the failure occurred is
automatically used, unless it has been excluded from hot-relocation use.
◆ To exclude a disk from hot-relocation use, see “Excluding a Disk from Hot-Relocation
Use” on page 236.
◆ To make a disk available for hot-relocation use, see “Making a Disk Available for
Hot-Relocation Use” on page 237.