1. A computer system comprising: a storage system comprising one or more disk drives that store data and a disk controller that controls reading data from, and writing data to, said one or more disk drives; and a computer comprising a buffer memory that stores data to be stored on said one or more disk drives and a processor, said computer being connected to said storage system, wherein said processor receives an access request to be issued to a file stored on said one or more disk drives, updates data stored in said buffer memory according to the access request, creates first information and sends the first information to said disk controller, said first information including updated data updated in the buffer memory, and sends second information to said disk controller, said second information requesting to update data stored in a storage area of said storage system and wherein said disk controller uses the updated data included in the first information to update data stored on said disk drives