US Patent 7937482 Scalable consensus protocol

In one embodiment, a system comprises a plurality of nodes coupled to a network. At least a subset of the nodes are configured to maintain a replica of a state machine. The nodes are classified into a plurality of non-overlapping classes. A first class comprises at least one node that is a current participant in a consensus protocol to control transitions of the state machine. A second class comprises nodes that are not current participants in the consensus protocol but which are reclassifiable into the first class. The node(s) in the first class are configured to act on a proposal for a transition of the state machine according to the consensus protocol.