You can run Docker on a single PC, which is what I've done so far in this book, and it's how you would work with Docker in development and basic test environments. In more advanced test environments and in production, a single server isn't suitable. For high availability and to give you the flexibility to scale your solutions, you need multiple servers running as a cluster. Docker has cluster support built into the platform, and you can join several Docker hosts together using Docker Swarm mode.
All the concepts you've learned so far (images, containers, registries, networks, volumes, and services) still apply in swarm mode. Docker Swarm is an orchestration layer. It presents the same ...
