Patent ID: 7600152

Claim:
A method of operating a storage controller for interfacing between a plurality of host systems and a direct access storage devices system, the storage controller including a first cluster including a first processor and a first cache, and a second cluster including a second processor and a second cache, the method comprising: directing data from the host systems through first and second data paths in the storage controller to the direct access storage system, wherein the first processor and the first cache are associated with the first data path, and the second processor and the second cache are associated with the second data path; under a first set of defined conditions, entering into a failover mode, wherein data directed to the first data path are routed to the second data path; and under a second set of defined conditions, deconfiguring the first cache without entering the failover mode; and wherein the first cache includes a series of tracks, a series of memory pages on said tracks, and a multitude of segment control blocks, and wherein the deconfiguring includes identifying selected pages to be removed from the first cache, all of said selected pages being on the same one of said tracks, and storing in one of the segment control blocks an ID of said one of said tracks.