A hot spare pool is an ordered list (collection) of hot spares.
You can place hot spares into one or more pools to get the most flexibility and protection from the fewest slices. That is, you could put a single slice designated for use as a hot spare into multiple pools, each hot spare pool having different slices and characteristics. Then, you could assign a hot spare pool to any number of submirror volumes or RAID 5 volumes.
You can assign a single hot spare pool to multiple submirrors or RAID 5 volumes. On the other hand, a submirror or a RAID 5 volume can be associated with only one hot spare pool.
When I/O errors occur, Solaris Volume Manager checks the hot spare pool for the first available hot spare whose size is equal to or greater than the size of the slice that is being replaced. If found, Solaris Volume Manager changes the hot spare's status to “In-Use” and automatically resynchronizes the data. In the case of a mirror, the hot spare is resynchronized with data from a good submirror. In the case of a RAID 5 volume, the hot spare is resynchronized with the other slices in the volume. If a slice of adequate size is not found in the list of hot spares, the submirror or RAID 5 volume that failed goes into a failed state and the hot spares remain unused. In the case of the submirror, the submirror no longer replicates the data completely. In the case of the RAID 5 volume, data redundancy is no longer available.