Patent ID: 6282671
Filing Date: 2001-08-28
Classification: G06F,H03M

Abstract:
A method for improved efficiency of parity calculation in a RAID data storage system having a cache memory, said method comprising the steps of:in response to each writing of updated data to replace old data within said RAID data storage system wherein said updated data does not span an entire data stripe:predetermining a number of input/output operations required to calculate an RMW new parity value utilizing an old parity value; said old data; and, said updated data;predetermining a number of input/output operations required to calculate an XOR new parity value utilizing said updated data and all remaining old data within said entire data stripe; anddetermining if data sequentially preceding said updated data is present within said cache memory;calculating an RMW new parity value only if calculation of said RMW new parity value requires fewer input/output operations and data sequentially preceding said updated data is not present within said cache memory; andcalculating an XOR new parity value if calculation of said XOR new parity value requires fewer input/output operations or said data preceding said updated data is present within said cache memory wherein RAID data storage system performance is optimized.