What is State Machine Replication (SMR)?

State Machine Replication (SMR) is a general approach in distributed computing for building fault-tolerant systems. This is achieved through the replication of servers (states or state machines) and organization of client exchanges with server replicas. SMR accomplishes this by deploying copies of a web service across a set of servers rather than just one. This approach can potentially increase a system's performance and capacity since the replicas provide more resources to the service, while achieving operational fault tolerance through the elimination of a single point of failure.