Performance management and fault tolerance are two important issues faced by computing systems research. In this dissertation, we exploit the use of feedback control for performance management and fault tolerance. Specifically, we propose Queueing Model Based Feedback Control scheme to achieve performance regulation. It integrates the ``descriptive'' power of queueing theory and the ``prescriptive'' power of feedback control to control computing system's performance. In the second part of this dissertation, we further exploit the use of feedback control to achieve fault tolerance for real-time embedded control systems. We propose ORTEGA (On-demand Real-TimE GuArd), a new fault tolerance architecture which utilizes feedback control based software execution. It can be deployed in a wide range of real-time embedded applications to provide fault tolerance. We implemented ORTEGA in an inverted pendulum testbed to demonstrate its efficacy and efficiency. Based on the ORTEGA design, we discuss the fault tolerance and scheduling co-design problem and its solutions.