Patent ID: 6513142
Filing Date: 2003-01-28
Classification: G06F

Abstract:
A system for detecting and acting upon unchanged parity in a write operation, wherein an original block of data and associated original parity block are each stored at respective predetermined storage location in a storage disk array and wherein a new block of data is to be written to the respective predetermined storage location, the system comprising:a cache memory for caching blocks of data and associated parity blocks written from a host processor prior to writing thereof in the disk array and for caching blocks of data and associated parity blocks read from the disk array prior to transfer thereof to the host processor; a cache manager for controlling caching of the blocks of data and associated parity blocks in the cache memory and transfer of the blocks of data and associated parity blocks to and from the disk array; a direct memory access and exclusive-OR (DMA/XOR) engine that transfers the blocks of data and associated parity blocks between each of the host processor, cache memory and disk array, the DMA/XOR engine being constructed and arranged to perform an XOR function combining the original block of data read from the disk and cached in the cache memory with the new block of data written from the host and cached in the cache memory to thereby derive a first result and to further perform an XOR function combing the first result with the original parity block to thereby derive a data difference result; and a detector that determines whether the data difference result equals either of a zero or a non-zero value, wherein a predetermined optimization function is performed when the data difference result equals zero.