A computer system according to one preferred embodiment of the present invention has a server and a storage subsystem, wherein the server is configured to enable data write to a cache area of the storage subsystem. Further, the server manages the usages of the cache area. When storing data from the server to the cache area, the server determines whether a data-writable area exists in the cache area or not. If there is a writable area, data is stored in the writable area.