Redundant Array of Inexpensive Disks – parallel array with ECC. Level 2 introduces hamming code error checking across the disks. This introduces the possibility of data recovery without a complete duplication of data, although it does require several check disks. This also requires that all disks in a group be accessed, even for small transfers, and the process has to wait for the slowest to finish before the transfer is complete. See also RAID.