A computer system functions to dynamically assign the storage capacity to the host computer. If an event such as a failure occurs in the logical resources, the performance requirements of the virtual volumes must be guaranteed to the host computer.Accordingly, the computer system comprising a storage apparatus, wherein the storage apparatus detects the occurrence of an event in the logical resources, compares the performance of the logical resources where the event occurred with the performance of the virtual volumes and, in accordance with the result of the comparison, sets the correspondence relationship of the virtual volumes to the logical resources.