A hot spare pool is a collection of slices (hot spares) reserved by DiskSuite to be automatically substituted in case of a slice failure in either a submirror or RAID5 metadevice. Hot spares provide increased data availability for mirrors and RAID5 metadevices.
Hot spare pools are used by mirrors and RAID5 metadevices. In the case of a mirror, the hot spare pool is associated with the submirrors.
A hot spare slice can be assigned to one or more hot spare pools.
A hot spare pool can be associated with multiple submirrors or RAID5 metadevices. However, a submirror or RAID5 metadevice can only be associated with one hot spare pool.
Replacement is based on a first fit for the failed slice, and follows the order specified in the hot spare pool.
Hot spares are not intended to remain a permanent part of your configuration. They need to be replaced with repaired or new slices.
Hot spares cannot contain state database replicas.
Ideally, slices added to the hot spare pool should be attached to different controllers. This ensures availability of data due to controller error or failure.
Do not associate hot spares of the wrong size with submirrors or RAID5 metadevices.
Do not assign a hot spare pool to a submirror in a one-way mirror.
Do not have all hot spares within a hot spare pool marked as in-use. If this happens, either add additional hot spares to the hot spare pool, or repair the slices that have been hot spare replaced.
Hot spare pools may be allocated, deallocated, or reassigned at any time unless a slice in the hot spare pool is being used to replace an errored slice in a metadevice it is associated with.