A computer system which enables more efficient use of a storage system shared by plural host computers and optimizes the performance of the whole system including the host computers and storages. A computer device has a first control block which logically partitions computing resources of the computer device and makes resulting partitions run as independent virtual computers. The storage system has a second control block which logically partitions storage resources of the storage system and makes resulting partitions run as independent virtual storage systems. The system also has a management unit incorporating: a first control table which controls computing resources of the computer device; a second control table which controls storage resources of the storage system; and a third control table which controls the relations between the virtual computers and the virtual storage systems. The first control block logically partitions the computing resources according to the first control table; and the second control block logically partitions the storage resources according to the second control table.