11.2.11 Considerations regarding the number of manager nodes It is vital to understand how swarm mode’s fault-tolerance feature works to prevent problems  with your cluster service. Although it is possible to run a cluster with only one manager node,  this approach is not ideal for organizations that have high-availability policies. If the  single-node manager fails, the services continue to process the user requests. However, you  must create a cluster to recover the manager node operations. Docker uses a consensus algorithm that is named  raft  to achieve internal consistency across  the entire swarm cluster and all containers that are running on it. Docker recommends that  you implement an odd number, based to your high-availability requirements, according to the  following rules: GLYPH<SM590000> A three-manager swarm tolerates a maximum loss of one manager. GLYPH<SM590000> A five-manager swarm tolerates a maximum simultaneous loss of two manager nodes. GLYPH<SM590000> An N-manager cluster tolerates the loss of at most (N-1)/2 managers. Chapter 11. Swarm on zCX  251 2/4: running [==================================================>]  3/4: running [==================================================>]  4/4: running [==================================================>]  verify: Service converged  admin@570e9473805e:~$  docker service ls ID NAME MODE REPLICAS IMAGE PORTS pwu25hj3wpww webserver replicated 4/4 nginx:latest *:80->80/tcp For more information about the cluster algorithm, see this web page.