Redundant Array of Independent Disks
The original ("..Inexpensive..") term referred to the 3.5 and 5.25 inch disks used for the first RAID system but no longer applies. As solid state drives are becoming a practical repacement for magnetic disks, "RAID" is sometimes expanded as "Redundant Array of Independent Drives".
The following standard RAID specifications exist:
RAID 0 Non-redundant striped array RAID 1 Mirrored arrays RAID 2 Parallel array with ECC RAID 3 Parallel array with parity RAID 4 Striped array with parity RAID 5 Striped array with rotating parity
RAID originated in a project at the computer science department of the University of California at Berkeley, under the direction of Professor Katz, in conjunction with Professor John Ousterhout and Professor David Patterson. A prototype disk array file server with a capacity of 40 GBytes and a sustained bandwidth of 80 MBytes/second was interfaced to a 1 Gb/s local area network. It was planned to extend the storage array to include automated optical disks and magnetic tapes.