A hot spare pool is an ordered list (collection) of slices (hot spares) that DiskSuite uses to provide increased data availability for mirrors and RAID5 metadevices. A hot spare is reserved by DiskSuite to be automatically substituted in case of a slice failure in either a submirror or RAID5 metadevice.
A hot spare cannot be used to hold data while it is idle. A hot spare must remain ready for immediate use in the event of a slice failure in the metadevice with which it is associated. Because of the way in which hot spares operate, an additional investment in disks is necessary.