What is a requirement for a RAID array?

A RAID (Redundant Array of Independent Disks) array requires multiple identical drives, with a minimum of two drives that are the same size. This is because RAID configurations rely on distributing data across multiple disks to improve performance and provide redundancy in case of a drive failure. Using identical drives ensures that the RAID can effectively manage striping or mirroring data without wasted space, as differing drive sizes can lead to underutilization of available storage.

For example, in RAID 1 (mirroring), data is duplicated across two drives, so having drives of the same size prevents scenarios where only part of the capacity of the larger drive can be used. Similarly, in RAID 0 (striping), while there’s no redundancy, the performance benefits are maximized when the drives are the same size to balance the load evenly. In summary, having at least two identical drives is essential for achieving the intended functionality and benefits of RAID arrays.