This metric category represents the statistics related to the spare disks in a RAID (Redundant Array of Independent Disks) group. A RAID group consists of a parity disk, up to 28 data disks, and optional spare disks.
A spare disk in an auxiliary disk used to replace other disks should they become corrupted or full. When a disk in a RAID group fails, a spare disk automatically replaces it. Spare disks are all the disks in the systems that have not been assigned to a volume.
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