Understanding RAID Levels: From RAID 0 to RAID 10 and Beyond

RAID (Redundant Arrays of Independent Disks) combines multiple independent disks into a single logical array to improve I/O performance and data reliability, addressing the limitations of single‑disk storage such as low throughput, limited capacity, and high failure risk.

JBOD (Just a Bunch Of Disks) refers to configurations outside RAID, where disks are either managed individually or concatenated to form a larger logical volume without redundancy.

RAID 0 stripes data across at least two disks, delivering near‑linear read/write speed gains but offering no fault tolerance; a single disk failure results in total data loss.

RAID 1 mirrors data on at least two disks, providing high redundancy at the cost of 50% storage efficiency.

RAID 5 distributes parity information across at least three disks, balancing storage efficiency and fault tolerance while requiring extra CPU for parity calculations; it can survive one disk failure.

RAID 6 adds a second parity block, allowing up to two simultaneous disk failures but incurring higher computational overhead and reduced usable capacity; a minimum of four disks is required.

RAID 2, 3, 4 are rarely used in practice and mainly appear in research; RAID 7 is a proprietary, high‑performance solution from Storage Computer Corporation, typically priced significantly higher than standard RAID levels.

RAID N+N (e.g., RAID 01, 10, 50, 60) combines two RAID types by first creating arrays of one level and then layering another level on top, offering flexible trade‑offs but often at higher cost.