Storage system and method for controlling cache

A storage system coupled to a host system, comprising:

• a plurality of storage apparatuses,
• wherein each of the plurality of storage apparatuses is coupled to the host system,
• each of the plurality of storage apparatuses comprises a storage device and a cache memory area in which data input/output from/to the storage device is to be cached,
• each storage apparatus manages a cache memory area within any other storage apparatus coupled to the storage apparatus as well as a cache memory area within the storage apparatus and can input/output data to/from the cache memory area of any other storage apparatus,
• in the case where any one of the plurality of storage apparatuses receives an I/O (Input/Output) request in which an address of a logical volume is designated, at least one of the plurality of storage apparatuses determines a cache destination storage apparatus in which I/O data which is data conforming to the received I/O request is to be cached based on at least one of a target I/O pattern and a coupling mode,
• the target I/O pattern is an I/O pattern to which I/O conforming to the received I/O request belongs among a plurality of I/O patterns,
• each of the plurality of I/O patterns is a pattern relating to whether an I/O destination address in the logical volume is random or sequential, and
• the coupling mode indicates whether or not a storage apparatus which is to receive the I/O request is determined.