Abstract: A computer system that is composed of a host computer, a storage device and a management computer. The storage device comprises a port for connecting with the host computer, a cache memory, a processor, and a plurality of logic volumes which are logical memory regions. For each logic volume, the port, the cache memory and the processor are divided into logic partitions, as resources that are used for reading and writing in the logic volume. The host computer reads and writes with respect to the logic volumes. If a failure occurs in the storage device, the management computer issues a command to the storage device to allocate the resources of a logic partition for which reading/writing performance is not ensured to a logic partition for which reading/writing performance is ensured.