Abstract: A data processing system with a RAID cache disk subsystem utilizes three RAID cache disk controllers to provide increased performance along with increased reliability, especially in the event of a failure of one of the disk controllers. Disk writes are mirrored in two disk controllers in order to guarantee integrity in the event of a disk controller or interface failure. Typically this write caching must be terminated when one of the controllers fails in order to maintain integrity. In the present invention, write caching continues utilizing the two remaining disk controllers.