About managers Docker 1.12 swarm mode in production


I was checking the following statement in: https://blog.docker.com/2016/07/docker-built-in-orchestration-ready-for-production-docker-1-12-goes-ga/
“In production environments, we strongly recommend having nodes designated as either “managers” or “workers”. In this mode, managers do not execute containers, thus reducing their workload and attack surface.”

I couldn’t find info on recommended minimal requirements for manager nodes. Does anyone knows what would they be? Have anyone experienced the impact it may have to run tasks on managers in production environments?