Fault Tolerance for Outputs and Clients

We have already discussed how to make a group of state machines tolerant to faults. However, the output of the state machines goes to the output devices read by the voter devices. The output and voter devices can also fail. In this lesson, we will discuss how to deal with such failures.

Fault-tolerant outputs

If we use a single output device for an ensemble of replicas, the resulting system would not be $t$ fault-tolerant. This is because the failure of this node can result in the system being unable to generate correct outputs. Let's see how we can provide fault tolerance in this scenario:

Outputting externally

A major proportion of applications of state machine replication requires outputting to a client, system, or node not part of the group of replicas. Suppose a system of replicated state machines has an output node that collects outputs from all replicas and sends the combined output to its destination. In that case, failure of the ...