Which RAID configuration requires three mass storage devices for redundancy?

RAID 5 is a configuration that provides redundancy through the use of disk striping with parity. It requires a minimum of three storage devices to function effectively. In RAID 5, data is split across all the drives in the array, along with parity data which is used to reconstruct information in the event of a single drive failure. This means that if one drive fails, the system can still operate normally, and no data is lost thanks to the parity information stored on the other drives.

The requirement for three devices is pivotal; one of them is used for parity, while the other two hold portions of the actual data. This configuration balances performance, storage efficiency, and fault tolerance, making it a widely used RAID setup in environments that demand reliability without sacrificing too much speed.

In contrast, configurations like RAID 0 do not offer any redundancy and require a minimum of two drives. RAID 1, while providing redundancy by mirroring data across two drives, does not require three drives either. RAID 10 combines mirroring and striping, requiring at least four drives for its operation. Hence, RAID 5 distinctly stands out as the only option that necessitates three drives for providing redundancy through its unique parity scheme.