According to the present invention, it is possible to rearrange an arrangement unit on an appropriate storage device at a more appropriate timing in a complex computer system. A computer system according to the present invention includes a plurality of storage devices of different performance, and provides a virtual volume, the storage devices allocating a segment of the plurality of storage areas to an arrangement unit, which constitutes the target of a virtual volume, in accordance with the arrival of a write request from the business server, and managing, on the business server, an execution time and a predicted execution time of a job to be executed, and a time at which the storage area segment was allocated to the arrangement unit, inferring the relationship of the arrangement unit and the job from the job execution time and the time at which the storage area segment was allocated, and changing the storage area segment allocated to this arrangement unit to another storage area segment at a time decided based on the specified relationship and the predicted execution time.