A computer system comprising a plurality of servers and a management server, wherein the plurality of servers include a plurality of service servers having an application executing a predetermined service, and a storage server storing therein data used by the application, wherein each of the plurality of service servers includes a first processor, a first memory coupled to the first processor, a first cache device in which a server cache for temporarily storing data is set up, coupled to the first processor, and a first interface for coupling to another apparatus coupled to the first processor, wherein the storage server includes a second processor, a second memory coupled to the second processor, a second cache device in which a storage cache for temporarily storing data is set up, coupled to second processor, a second interface for coupling to another apparatus coupled to the second processor, and a plurality of storage apparatuses (304, 305) each having an access performance different from one another, wherein the management server includes a third process or, a third memory coupled to the third processor, and a third interface for coupling to another apparatus coupled to the third processor, wherein the each of the plurality of service servers includes a first operating system for controlling a service server, wherein the first operating system includes a cache driver for controlling the server cache, wherein the storage server includes a second operating system for controlling the storage server, wherein the second operating system generates, via the plurality of storage apparatuses (304, 305), a plurality of tiered storage areas each having an access performance different from one another, and manages the plurality of tiered storage areas distinctively per performance thereof, wherein the management server includes a cache optimization part for transmitting a control instruction for arrangement of data on the storage server based on information transmitted from the cache driver, characterised in that the cache optimization part includes: an alert setting information generation part for generating alert setting information for the each of the plurality of service servers to transmit alert information notifying a trigger to change an arrangement of data in accordance with a state of the service, and for transmitting the generated alert setting information to the each of the plurality of service servers; and a control information generation part for generating at least one of cache control information including a first command for controlling an arrangement of cache data on the storage cache and tier control information including a second command for controlling an arrangement of the data on the plurality of tiered storage areas, and for transmitting control information including at least one of the cache control information and the tier control information to the storage server in a case of receiving the alert information from the cache driver of any of the service servers, wherein the cache driver of the each of the plurality of service servers transmits the alert information to the management server in case of detecting the trigger to change the arrangement of the data based on the alert setting information, and wherein the second operating system executes at least one of a cache control process for controlling the arrangement of the data on the storage cache and a tier control process for controlling the arrangement of the data on the plurality of tiered storage areas based on the control information received from the management server. an alert setting information generation part for generating alert setting information for the each of the plurality of service servers to transmit alert information notifying a trigger to change an arrangement of data in accordance with a state of the service, and for transmitting the generated alert setting information to the each of the plurality of service servers; and a control information generation part for generating at least one of cache control information including a first command for controlling an arrangement of cache data on the storage cache and tier control information including a second command for controlling an arrangement of the data on the plurality of tiered storage areas, and for transmitting control information including at least one of the cache control information and the tier control information to the storage server in a case of receiving the alert information from the cache driver of any of the service servers,