A computer system includes a management server which includes an acquisition unit for acquiring the configuration information and performance information of the storage apparatus and the host computer respectively at different timings, and a comparison unit for comparing, when a configuration change of the storage apparatus is commanded externally, a performance value of components in the storage apparatus subject to the configuration change and a performance value of components in a connection relationship with the components. The acquisition unit determines that an unknown component has been added in the storage apparatus when the difference in the performance values compared with the comparison unit exceeds a predetermined threshold, and reacquires configuration information from the storage apparatus.