A storage cluster including a first storage apparatus and a second storage apparatus is defined. Communication between the first storage apparatus and the second storage apparatus uses a first network and an access request from a host computer uses a second network. Each of the first and second storage apparatuses defines internal LUs by using storage devices included in that storage apparatus. The first storage apparatus defines other internal LUs by using internal LUs of the second storage apparatus and the second storage apparatus defines other internal LUs by using internal LUs of the first storage apparatus.