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Commands for Hot RelocationThe 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:
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 RelocationOne 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. 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 and the existing volumes comprised of the unaffected portions of the disk remain accessible. When selecting space for relocation, hot relocation preserves the redundancy characteristics of the Volume Manager object that the relocated subdisk belongs to. 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 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. When hot relocation takes place, the failed subdisk is removed from the configuration database and Volume Manager takes precautions to ensure that the disk space used by the failed subdisk is not recycled as free space. |
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