Unlike "Global Hot Spare" which can be used with any RAID groups, Dedicated Hot Spare can only be used with a specific RAID group. When a disk drive fails in the RAID group with a Dedicated Hot Spare is pre-set, data on the disk drive is rebuild automatically on the dedicated hot spare disk. Then after the failed disk drive is replaced with a new disk drive, data on the dedicated hot spare disk will be retrieved (copied back) onto the new disk automatically. Dedicated Hot Spare is a special case of Global Hot Spare for use in Dedicated Mission Critical environments where sharing is insufficient security.