Some embodiments provide a control system for managing a network that includes several switching elements managed by the control system. The system includes several controller instances for managing the switching elements. Each particular controller instance includes a coordination manager for communicating with the coordination managers of the other controllers in order to partition control of the plurality of switching elements by electing a master controller for different sets of switching elements. The particular controller instance also includes a storage for storing control data for controlling the set of managed switching elements managed by the controller instance, and a switch interface for passing the control data to the set of managed switching elements.