Patent ID: 7343451

Claim:
A disk array device comprising: a channel adapter connected to a host device and an external device via a communications port for controlling the exchange of data with the host device and said external device; a disk adapter for controlling the exchange of data with a memory device; a cache memory used by said channel adapter and said disk adapter; one or more logical system partitions (SLARs) which are constructed by logically dividing resources provided by said channel adapter, said disk adapter, said memory device and said cache memory, each of said logical system partitions including cache logical partitions (CLARs) formed by logically dividing said cache memory; wherein at least one of said channel adapter and said disk adapter assigns segments to each of said cache logical partitions so that a respective one of said cache logical partitions exclusively utilizes assigned ones of said segments, wherein said channel adapter assigns said segments, if said segments are guaranteed according to write requests from the host device, wherein said disk adapter assigns said segments, if said segments are guaranteed according to read requests from the host device, wherein said at least one of said channel adapter and said disk adapter calculates a number of said segments required for processing a write or read request issued by the host device, and specifies a corresponding said cache logical partition based upon the information for a logical unit for which access was requested by the host device, wherein said at least one of said channel adapter and said disk adapter compares a number of said segments in use managed by a cache managing table and a cache capacity managed by a CLPR managing table, and if the number of said segments in use is smaller than the cache capacity of the CLPR, said at least one of said channel adapter and said disk adapter compares the number of said calculated segments required for processing with a number of free segments.