Provided is a storage system superior in fault tolerance. This storage system is composed of a controller having a plurality of processors and other units. When an error occurs in any one of the components in the controller, the storage system cuts off an I/O path of the controller, specifies the failed component in the cutoff status, and invalidates such failed component. Further, after invalidating the failed component, the storage system determines whether it is operable only with the normal components, cancels (releases) the cutoff of the I/O path when it determines that it is operable, and resumes operation by rebooting itself.