Abstract: A fault tolerant, magnetic disk drive array with error detection and correction. The present invention performs vertical parity checks and one or two additional diagonal parity checks on a data stream as it is read into a disk drive array. The results of these "read-in" parity checks are stored in either two or three redundant disk drives. Upon read out of the data stream from the disk drive array, similar "read-out" parity checks are performed on the data. Based upon a comparison of the "read in " and read "out" vertical and diagonal parity checks, corrupted data can be detected and corrected.