Patent ID: 7765217

Claim:
A storage system comprising: at least one client; a plurality of file servers connected to the client through a network, each of said file servers including a storage device, for providing a response to a request from the client; and control means for deriving an access context of data in one of said plurality of storage devices accessed from the client, for migrating to another one of said storage devices provided in the vicinity of the client, the data whose access context satisfies a migration condition defined in advance, and for performing rearrangement of the data, wherein said deriving is performed using a plurality of types of operations, wherein said control means comprises a switch device logically disposed between the client and each of the file servers; said switch device comprising: means for unifying storage resources of the file servers; data migration means for performing the rearrangement of data among the file servers with data access service to the client not stopped; means for associating an execution log for each type of the types of operations with regard to a data reading request, a data updating request, a data delete request, and a name changing request among requests from the client with at least one of a date and time when the operation has been executed, a name of a user who has executed the operation, a name or an address of a client that has executed the operation, a name or an address of a file server that has executed the operation, and a pathname of a file on which the operation has been executed, for storage in storage means; and means for deriving the access context of the file or a directory from the stored execution log, wherein based on log information on a file access, said means for deriving the access context changes a point and a weighting factor per the access according to the type of the operation on the file and information at a time when the operation is performed, and calculates the access context having a value in accordance with a characteristic of the file indicating whether the file is being currently created or the file has been already completed.