An apparatus creates an extended configuration proposal of a storage system including multiple nodes. A processor of the apparatus is configured to acquire information on requested performance of each host, which accesses the storage system. The processor is configured to acquire information on performance of each of multiple existing nodes of the storage system. The processor is configured to determine a number and performance of one or more additional nodes and a coupling form between the host and the storage system so as to satisfy the requested performance of each host. The processor is configured to include the number and the performance of the one or more additional nodes and the coupling form in the extended configuration proposal.