Patent ID: 8161235

Claim:
A storage system including a server, and a storage subsystem connected to said server and having a hard disk drive storing a plurality of files, said server comprising: a disk cache for temporarily storing data to be sent to said storage subsystem; and a server controller controlling said server, said storage subsystem comprising: a controller cache for temporally storing data sent from said server, to be written to said hard disk drive in said storage subsystem, and a subsystem controller controlling said storage subsystem, wherein, the storage system manages the respective addresses of said disk cache, said controller cache and said hard disk drive storing the same file, wherein, when said storage system executes a file erasing process for a certain file of said plurality of files by respectively overwriting said certain file stored in respective addresses of said disk cache, said controller cache and said hard disk drive with a plurality of erasing data including a first erasing data and a second erasing data, wherein said subsystem controller manages whether or not data stored in said controller cache is already written to said hard disk, and wherein said server controller is configured to: judge if said first erasing data stored in said controller cache is already written to said hard disk based on a communication with said subsystem controller, send, if said first erasing data is already written to said hard disk according to the judgment, said second erasing data in said disk cache to said storage subsystem so that the subsystem controller can write not only said second erasing data but also said first erasing data to said hard disk drive.