Patent ID: 7281087

Claim:
A disk array device having cache memory and accessed by hosts, wherein cache segment identifiers and access groups are defined for managing the cache memory by dividing all area of said cache memory into a plurality of cache segments, each corresponding to an access group, said disk array device comprising: a segment information management table comprising a segment management table that manages, for each cache segment identifier, a division size criterion value for the cache segment; and an access group management table that manages information on a correspondence between the access groups and the cache segments; a cache management table managing information on a link status of LRU (Least Recently Used) links provided one for each cache segment for controlling data discarding from the cache memory; segment information setting means that sets information in said segment information management table based on a setting command from a host; and input/output management means that, based on settings in said segment information management table and the link status of LRU links corresponding to the cache segments managed in said cache management table, identifies to which access group an input/output request from a host corresponds and that, considering a division size allocated to each cache segment, controls discarding data from the cache memory of each cache segment; wherein data is discarded from a first cache segment that stores data in excess of an allocation criterion value associated with the first cache segment, and wherein data is newly written to a second cache segment based on a determination that the second cache segment stores less data than an allocation criterion value associated with the second cache segment.