1. A storage system coupled to host computers, comprising: a plurality of disk drives; a plurality of processors, each controlling data reception and data transmission between the host computers and the disk drives; a shared memory for storing control information; and a plurality of shared memory control units provided for a plurality of the processors, respectively, for controlling access to the shared memory from the processors, wherein the processor transmits a plurality of first requests to the shared memory control unit that is provided for the processor and transmits second requests, each first request initiating the access to the shared memory, the shared memory control unit receiving the first requests accesses the shared memory a plurality of times substantially at the same time and returns an access result derived by the access to the shared memory to the processor receiving the request in response to the second requests.