Also from DockerCon 2017, fellow Docker Captain and friend Laura Frank had a great session on the internals of Swarm Managers and how quorum of their Raft log works, called "Everything You Thought You Already Knew About Orchestration". She goes into the math of how you always need an odd number of Managers, and what happens when one or more fail.

She then shows various recovery options in case you "loose quorum" in your Swarm cluster. This video is demo heavy, so it's worth watching the whole thing!

Watch on YouTube: https://www.youtube.com/watch?v=Qsv-q8WbIZY