To manage the configuration of a data archiving system without increasing the load on the data archiving system while keeping the performance of computers and the load on storage subsystems balanced, there is provided a computer system, including: a plurality of data archiving servers; a storage subsystem which provides storage extents to the plurality of data archiving servers; and a management computer. The management computer manages data archiving server performance management information, which holds information about performance of the plurality of data archiving servers, and storage utilization information, which holds information about load on the storage extents. The management computer changes the association between the data archiving storage extents and the storage extents based on a data archiving server performance management information and a storage utilization information.