Method and means for managing disk drive level logic and buffer modified access paths for enhanced raid array data rebuild and write update operations

A method and means for performing logical-combining functions such as XOR operations in a RAID 3 or 5 array or a combinational configuration of disk drives. The logical combining occurs below the device attachment interface and is used in generating new parity for write update operations and data rebuilding. Each disk drive is modified to use a segmented and address synchronized buffer in the write and read paths, and a logical circuit that combines the data in the write path before buffering with the data in the read buffer as it is read out from the buffer. The logically combined result is presented at the device read path interface. The combined data from a first disk drive interface is introduced into the write path of a second path through the second device interface and the logical combining repeated ad seriatim, the device interfaces being connectable in a daisy-chain manner and configurable by array controller commands.