- You can’t implement consistent storage and respond to all requests if you might drop messages between processes. This is the CAP theorem.In other words you can build a system which is either available or consistent when network partition happens.
- Consensus is impossible to implement in such a way that it both a) is always correct and b) always terminates if even one machine might fail in an asynchronous system with crash-* stop failures
- Consensus is impossible to solve in fewer than 2 rounds of messages in general.
- Atomic broadcast is exactly as hard as consensus – in a precise sense, if you solve atomic broadcast, you solve consensus, and vice versa
