Patent ID: 7730275

Claim:
A computer system comprising: a plurality of storage systems having a plurality of disk units which are configured into a plurality of physical storage regions for storing data and a storage controller which provides data files to at least one of a plurality of external devices via a network; a plurality of host computers coupling to at least one of the storage systems via a network and accessing data files for using the data, the data files being provided by at least one of the storage systems; and a management computer coupling the host computers and the storage systems via network, wherein said management computer checks a period between a present time and a predetermined time for data in a first data file, the predetermined time being later than the present time and sends to the storage system, an instruction for migration of the data to a second data file from the first data file according to the period, wherein a property of the second data file is different from that of the first data file, and wherein the storage system migrates the data responsive to the instruction.