Patent ID: 7373469

Claim:
A computer system, comprising: a computer which has an interface, a processor and a memory; a plurality of storage systems each of which has an interface, a processor and a memory; and a management computer for managing the computer and the plurality of storage systems, which has an interface, a processor and a memory, wherein: the plurality of storage systems include a first storage system, a second storage system, and a third storage system; the first storage system is coupled to the computer and the second storage system, and comprises a first storage area for storing data written by the computer; the second storage system is coupled to the first storage system and the third storage system, and comprises a second storage area to which the data stored in the first storage area migrates; the third storage system is coupled to the computer and the second storage system, comprises a virtual storage area corresponding to the second storage area, converts an access request to the virtual storage area into an access request to the second storage area, and issues the converted access request to the second storage system; and the management computer transmits, to the third storage system, a migration instruction to migrate the data migrated to the second storage area to a third storage area created in the third storage system based on a determination result between a value of the data migrated to the second storage area and a predetermined threshold value.