The present invention is a clustered storage system with which, even when access to the processor of another controller is sent from the processor of one controller, the processor of the second controller is able to prioritize processing of this access so that I/O processing is also prevented from being delayed. With the storage system of the present invention, the first processor of the first controller transmits request information which is to be processed by the second processor of the second controller to the second processor by differentiating between request information for which processing is to be prioritized by the second processor and request information for which processing is not to be prioritized, and the second processor acquires the request information by differentiating between request information for which processing is to be prioritized and request information for which processing is not to be prioritized.