A cluster is a group of machines connecting together to do work. A Docker host is a physical or virtual machine with the Docker Engine installed. We create a Docker Swarm cluster by connecting many Docker hosts together. We refer to each Docker host as a Docker Swarm node, simply a node.
In version 1.12, Docker introduced Swarm mode, a new orchestration engine to replace the old Swarm cluster, which is now referred to as Swarm classic. The main difference between Swarm classic and Swarm mode is that Swarm classic uses an external service, such as Consul, etcd, or Apache ZooKeeper as its key/value store, but Swarm mode has this key/value built in. With this, Swarm mode keeps orchestration latency at a minimum, and is more robust than Swarm classic because it does not need to interact with an external store. The monolithic nature of Swarm mode is...
