Hot spares provide extra protection for redundant volumes (RAID-1 and RAID-5) to help guard against data loss. By associating hot spares with the underlying slices that comprise your RAID-0 submirrors or RAID-5 configuration, you can have the system automatically replace failed slices with working slices from the hot spare pool. Those slices that were swapped into use are updated with the information they should have. The slices then can continue to function just like the original slices. You can replace the failed slices at your convenience.