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380 Administering hot-relocation
How hot-relocation works
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.
Note: 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:
When vxrelocd detects such a failure, it performs the following steps:
■ vxrelocd informs the system administrator (and other nominated users) by
electronic mail of the failure and which VxVM objects are affected.
See “Partial disk failure mail messages” on page 383.
See “Complete disk failure mail messages” on page 384.
See “Modifying the behavior of hot-relocation” on page 395.
■ vxrelocd next determines if any subdisks can be relocated. vxrelocd
looks for suitable space on disks that have been reserved as hot-relocation
Disk failure This is normally detected as a result of an I/O failure from a
VxVM object. VxVM attempts to correct the error. If the
error cannot be corrected, VxVM tries to access
configuration information in the private region of the disk.
If it cannot access the private region, it considers the disk
failed.
Plex failure This is normally detected as a result of an uncorrectable I/O
error in the plex (which affects subdisks within the plex).
For mirrored volumes, the plex is detached.
RAID-5 subdisk failure This is normally detected as a result of an uncorrectable I/O
error. The subdisk is detached.