(54) FAILOVER AND FAILBACK OF WRITE CACHE DATA IN DUAL ACTIVE CONTROLLERS
(75) Inventors: Clark E. Lubbers, Colorado Springs,
CO (US); Michael D. Walker, Colorado
Springs, CO (US); Susan G. Elkington,
Colorado Springs, CO (US)
(73) Assignee: Seagate Technology LLC, Scotts Valley, CA(US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl.No.: 11/479,846
(22) Filed: Jun. 30, 2006
(65) Prior Publication Data
US 2008/0005614 Al Jan. 3, 2008
(51) Int. CI.
(52) U.S. CI 714/5
(58) Field of Classification Search 714/6,
714/11, 5; 711/135 See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
5,790,775 A * 8/1998 Marks et al 714/9
6,006,342 A * 12/1999 Beardsley et al 714/5
6,513,097 Bl* 1/2003 Beardsley et al 711/113
A data storage system is provided with a pair of controllers and circuitry configured for failing back from a single active write back mode to a dual active write back mode by copying cached data directly from a cache of a survivor controller of the pair of controllers to a cache of the other controller. A method is provided for failing over from a dual active mode of first and second controllers to a single active mode of the first controller by relying on previously mirrored cache data by the second controller; reinitializing the second controller; and failing back to the dual active mode by copying cached data directly from the first controller to the second controller.
19 Claims, 8 Drawing Sheets