Hot-relocation guidelines
Hot-relocation automatically restores redundancy and access to mirrored and RAID-5 volumes when a disk fails. This is done by relocating the affected subdisks to disks designated as spares and/or free space in the same disk group.
The hot-relocation feature is enabled by default. The associated daemon, vxrelocd, is automatically started during system startup.
Refer to the following guidelines when using hot-relocation.
-
The hot-relocation feature is enabled by default. Although it is possible to disable hot-relocation, it is advisable to leave it enabled. It will notify you of the nature of the failure, attempt to relocate any affected subdisks that are redundant, and initiate recovery procedures.
-
Although hot-relocation does not require you to designate disks as spares, designate at least one disk as a spare within each disk group. This gives you some control over which disks are used for relocation. If no spares exist, Veritas Volume Manager uses any available free space within the disk group. When free space is used for relocation purposes, it is possible to have performance degradation after the relocation.
-
After hot-relocation occurs, designate one or more additional disks as spares to augment the spare space. Some of the original spare space may be occupied by relocated subdisks.
-
If a given disk group spans multiple controllers and has more than one spare disk, set up the spare disks on different controllers (in case one of the controllers fails).
-
For a mirrored volume, configure the disk group so that there is at least one disk that does not already contain a mirror of the volume. This disk should either be a spare disk with some available space or a regular disk with some free space and the disk is not excluded from hot-relocation use.
-
For a mirrored and striped volume, configure the disk group so that at least one disk does not already contain one of the mirrors of the volume or another subdisk in the striped plex. This disk should either be a spare disk with some available space or a regular disk with some free space and the disk is not excluded from hot-relocation use.
-
For a RAID-5 volume, configure the disk group so that at least one disk does not already contain the RAID-5 plex (or one of its log plexes) of the volume. This disk should either be a spare disk with some available space or a regular disk with some free space and the disk is not excluded from hot-relocation use.
-
If a mirrored volume has a DRL log subdisk as part of its data plex, you cannot relocate the data plex. Instead, place log subdisks in log plexes that contain no data.
-
Hot-relocation does not guarantee to preserve the original performance characteristics or data layout. Examine the locations of newly-relocated subdisks to determine whether they should be relocated to more suitable disks to regain the original performance benefits.
-
Although it is possible to build Veritas Volume Manager objects on spare disks (using
vxmake or the VEA interface), it is recommended that you use spare disks for hot-relocation only.
See "How hot-relocation works" on page 384.
