Patent ID: 7321986

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 system 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 define 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; wherein the first cache includes a series of memory pages, and the deconfiguring step includes the steps of; identifying selected pages of the first cache; marking each of said selected pages as unavailable; and after all of said selected pages unavailable, removing the selected pages from the first cache; wherein the memory pages are on a series of tracks in the first cache, and the first cache further includes a multitude of segment control blocks, each segment control block being associated with one of the memory pages, and a multitude of directory control blocks, each directory control block being associated with one of said tracks, and wherein: the selected pages are all on the same track; and the identifying step includes the step of, for each of the selected pages, identifying in the directory control block associated with the page, the segment control block associated with the page.