What is the function of a spare disk in a disk shelf?

• A. A spare disk is used for immediate hot spare function.
• B. Only used during firmware upgrades.
• C. A spare disk automatically replaces a failed disk in its RAID group to maintain redundancy.
• D. Spare disks are optional and not part of redundancy.

Answer: (C)

A spare disk serves as a ready substitute to maintain RAID redundancy. When a drive in a RAID group fails, the controller uses the spare to rebuild the data onto that disk, restoring the array’s fault tolerance. If the spare is configured as a hot spare, this replacement happens automatically what minimizes downtime and helps prevent data loss or performance degradation. Spare disks are an integral part of redundancy, not something used only during firmware upgrades or optional.