With the rapid development of Internet technology and the explosive growth of data, the storage system designed by tightly coupled hardware and software is limiting the development of storage technology severely, and unable to meet the fast changing needs in the mobile Internet and big data era increasingly. Software defined network (SDN) as new network architecture is more suitable for the development of the next-generation data centers. This paper proposes a new controller-based storage area network (SAN)—CSN architecture using the idea of SDN technology. CSN decoupling protocol control plane of FC switch from data plane deploys protocol control plane and distributed functions in the controller. At first, we introduce the architecture of CSN and discuss the specific design of controller for CSN in this paper. Then, the implement of communication and overall mechanism are described in detail. After that, CSN-based on-demand bandwidth-available first routing protocol is introduced and discussed. Finally, we verify the feasibility through the actual development environment. As a result of several experiments, server can establish a connection with the storage more quickly in CSN, and furthermore, CSN has better throughput and faster convergence, as well as more reliability and scalability. In addition, stress testing is conducted in the central controller for CPU, memory and bandwidth.