Patent ID: 8719524

Claim:
A storage system comprising: a plurality of volumes, each of the volumes is configured on a plurality of flash drives, each of the flash drives including a plurality of flash memory chips and a memory controller controlling reading/writing data to the plurality of flash memory chips; a cache memory configured to temporarily store data of the volumes; a plurality of processor packages, each of the processor packages including a processor configured to be in charge of processing access request to one of the volumes and including a local memory configured to store caching control information indicating whether data of the one of the volumes is stored in the cache memory or not; and a shared memory accessible from the processors, the shared memory storing the caching control information which is backup information of the caching control information stored in the local memory of each of the processor packages, wherein: in response to receiving a read request from a computer to a first volume, a first processor, which is in charge of the first volume, in a first processor package of the processor packages, is configured to update the caching control information in a first local memory in the first processor package, the first processor is configured to determine whether to reflect the update of the caching control information in the first local memory to the shared memory and whether to store read target data of the read request into the cache memory, and when the read target data is stored in one of the flash drives for providing the first volume, the first processor is configured to determine to transfer the read target data retrieved from the one of the flash drives to the computer without storing the read target data into the cache memory and without reflecting the update of the caching control information to the shared memory.