Video streaming has dominated traffic usage over the Internet. With the development of heterogeneous mobile devices, various streaming environments with different display sizes and network bandwidths have accelerated video streaming to the masses. To accommodate the increasing demand for video, streaming providers have made efforts to build services based on scalable video coding (SVC) over the cloud infrastructure, which leverages elastic amounts of resources and network bandwidth on the fly. In this paper, we suggest a split-layer SVC-based streaming architecture optimized for a cloud environment. By separately controlling streaming instances with awareness of clients device ratio amongst smartphone, tablet, and PC, we improve resource utilization and save network bandwidth. We also evaluate how our proposed system can improve the total cost for providing a video streaming service on a cloud infrastructure. We carry out extensive experiments to evaluate the performance in multiple real-life scenarios by simulating streaming services on (1) a mobile-client-heavy channel, (2) a PC-client-heavy channel, and (3) a device-balanced channel.