A spare disk must be initialized and placed in a disk group as a spare before it can be used for replacement purposes. If no disks have been designated as spares when a failure occurs, VxVM automatically uses any available free space in the disk group in which the failure occurs. If there is not enough spare disk space, a combination of spare space and free space is used.
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. The value of "closeness" depends on the controller, target, and disk number of 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.
If the failing disk is a root disk, hot-relocation only works if it can relocate all of the file systems to the same disk. If none are found, the system administrator is notified through email.
When hot-relocation takes place, the failed subdisk is removed from the configuration database, and VxVM ensures that the disk space used by the failed subdisk is not recycled as free space.