Asynchronous Reconfiguration for Paxos State Machines

This paper addresses reconfiguration of a Replicated State Machine (RSM) in an asynchronous system. It is well known that consensus cannot be solved in an asynchronous system. Therefore an RSM providing strong consistency, cannot guarantee progress in an asynchronous system. However, we show that reconfiguring the RSM is possible in a purely asynchronous system. This differs from all existing reconfiguration methods which rely on consensus to choose a new configuration. Since a reconfiguration to a new set of machines or even a different datacenter can serve to restore synchrony between replicas, asynchronous reconfiguration can also serve to increase the availability of an RSM.