Figure 1 illustrates the architecture of a single Chubby replica. A fault-tolerant replicated log based on the
Paxos algorithm sits at the bottom of the protocol stack. Each replica maintains a local copy of the log. The
Paxos algorithm is run repeatedly as required to ensure that all replicas have identical sequences of entries
in their local logs. Replicas communicate with each other through a Paxos-specific protocol.