Storage system and file-reference method of remote-site storage system

Abstract

A storage system conducting remote copy functions such that, when data is updated at a local site, contents of the update can be referred to in real time by storage at a remote site. A disk-control unit at a remote site receives file data written in accordance with an update of a file in a storage system at a local site and a history of the file-management information from the storage system at the local site and stores the data and the history. A file-system processing unit refers to the history and updates the file-management information in a file-system cache in accordance with the update of the file in the storage system at the local site. When a client issues a read request, the file-system processing unit refers to the file-management information updated in the file-system cache and transfers the contents of the update of the file to the client.

1 . 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.