Rejuvenating High Available Virtualized Systems

Virtualization technology in the form of server consolidation makes running of hot-standby replicas on one system possible, while software rejuvenation provides proactive recovery of failure. Both technologies have been used to make systems more dependable. However, the deployment of rejuvenation in virtualized systems had been limited only to virtual machines (VMs) or only to virtual machine monitors (VMMs), requiring changes to applications too. We propose a new rejuvenation technique for high available virtualized systems that is applied at both VM and VMM levels and yet it does not require any modifications to applications. Our proposition leverages the encapsulation of an application into a VM using this new combinatory rejuvenation technique that uses a time-based policy for VMM and a prediction-based policy for VMs. To demonstrate how much it can improve system availability, the stochastic reward net-based models of a typical virtualized consolidated server in cases of using a prediction-based policy, using a time-based policy, and using the proposed rejuvenation technique are presented and compared. We show that our method has higher system availability and lower downtime cost.