Patent ID: 6330642
Filing Date: 2001-12-11
Classification: G06F

Abstract:
A disk subsystem for use in a data processing system wherein the disk subsystem comprises:a first disk controller comprising:a first disk controller write cache; anda first means for coupling the first disk controller to a first host computer;a second disk controller bidirectionally coupled to the first disk controller and comprising:a second disk controller write cache,a first means for coupling the second disk controller to the first host computer;a third disk controller comprising:a third disk controller write cache,a first means for coupling the third disk controller to the first host computer;a set of disk drives logically comprising:a first set of logical disk drives and a third set of logical disk drives bidirectionally coupled to the first disk controller and the second disk controller;a fourth set of logical disk drives and a sixth set of logical disk drives bidirectionally coupled to the second disk controller and the third disk controller; anda second set of logical disk drives and a fifth set of logical disk drives bidirectionally coupled to the third disk controller and the first disk controller; andmeans for bidirectionally coupling the first disk controller to the second disk controller, the second disk controller to the third disk controller, and the third disk controller to the first disk controller;wherein:when in a first state which requires that the first disk controller, the second disk controller, and the third disk controller be active and able to communicate with the first host computer:the first disk controller provides write access to, write caching of, and delayed writing to the first set of logical disk drives and the second set of logical disk drives and provides write cache mirroring of the third set of logical disk drives and the fifth set of logical disk drives;the second disk controller provides write access to, write caching of, and delayed writing to the third set of logical disk drives and the fourth set of logical disk drives and provides write cache mirroring of the first set of logical disk drives and the sixth set of logical disk drives; andthe third disk controller provides write access to, write caching of, and delayed writing to the fifth set of logical disk drives and the sixth set of logical disk drives and provides write cache mirroring of the second set of logical disk drives and the fourth set of logical disk drives.