Virtual machine technology has been successfully applied for the construction of fault-tolerant computing systems. For example, vmware Fault Tolerance and Xen Remus support transparent failover of VMs running on different physical machines in a local area network. However, high availability alone is in many application domains not sufficient. Especially in the context of Cyber-Physical Systems, which interact with the physical environment, realtime constraints have to be fulfilled in order to avoid damage. Therefore, we are working on the combination of VM-based fault tolerance with a performance analysis technique, namely the modular performance analysis with real-time calculus. Such enhanced system would at any time be aware of its own performance and could use this information for smarter reconfiguration decisions in case of faults. This paper will sketch the underlying model, the envisioned system architecture, and discuss beneficial application scenarios.