Brief Announcement: Hierarchical Consensus

We introduce Hierarchical Consensus, an approach to generalizing consensus that allows us to scale groups beyond a handful of nodes, across wide areas. Hierarchical Consensus increases the availability of consensus groups by partitioning the decision space and nominating distinct leaders for each partition. Partitions eliminate distance by allowing decision-making to be co-located with replicas that are responding to accesses. A root quorum guarantees global consistency and fault tolerance. Hierarchical consensus is flexible locally, but improves upon prior approaches by balancing load, allowing fast replication across wide areas, and enabling consensus across large (> 100) systems of devices.