Patent ID: 7266644

Claim:
A storage system comprising: at least one disk to store data; a disk control unit to control writing and reading of data to and from said at least one disk; a disk cache for transmitting and receiving data to and from said at least one disk; a file server including a CPU, a main memory to store programs and data for said CPU, and a network interface to be coupled to clients through a network; and interfaces for sending and receiving data to and from other storage systems through a communication link; wherein said main memory includes a file system-processing unit managing storage areas of said at least one disk, so that files are correlated with data locations on said at least one disk, and a file-system cache to be used by said file system-processing unit; wherein said disk control unit receives data of a file that has been updated in another storage system and a history of file-management information through said communication link and stores the received data of a file and the history of file-management information on the disk; wherein said disk control unit refers to the history of the file-management information on the disk and updates file-management information in said file-system cache in accordance with the update of the file performed in said other storage system; and wherein, when said disk control unit receives a read request from a client coupled to the storage system, said disk control unit refers to the file-management information updated in said file-system cache and transfers the contents of the updated file to said client according to the file-management information, wherein said file system-processing unit comprises a metadata-update monitor monitoring the update of metadata, including data for file management, by referring to a journal log, including a history of said management information, and a metadata-updating unit updating the metadata in said file-system cache when said metadata-update monitor detects the update of a file.