Warning: these are design notes from initial stages of LogCabin and are are probably not relevant any longer.
One lesson from Paxos Made Live is that it's useful to have a way to compare replicas' state to verify that they are identical. Doing this periodically helped them discover bugs before they were exposed to applications. Ideally, LogCabin replicas could produce a single checksum value that would cover the entire contents of their state. This state includes: log entries, tombstones, and client responses (for linearizability). These same checksums could also be used to guard against disk corruption, by checking the consistency of servers before they are re-admitted to the cluster.
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