The storage system of the present invention has a simple configuration and ensures redundancy of the system. The primary storage control device and the first secondary storage control device are connected by a synchronous read method, and the primary storage control device and the second secondary storage control device are connected by an asynchronous read method. The primary storage control device sets a management number in the update data and saves a journal data. The primary storage control device associates the management number with the update data and transmits them to the first secondary storage control device. The first secondary storage control device writes the update data to the first secondary volume, associates the management number with the storage destination address of the update data and stores them in the maintenance table. If the primary storage control device stops, the first secondary storage control device becomes anew a primary storage control device. The first secondary storage control device is connected to the second secondary storage control device by an asynchronous read method.