Re: Differences from virtualisation?
That was certainly the explanation I heard from Red Hat this week - the CPU overhead for docker is less than 10% (typically about 5%, I think the figure was) and the memory overhead is much less too.
Plus, if there are multiple docker instances running and all looking at the same library then it'll use the library in the host rather than the docker image. If it's a different one on each instance, the instances will load their own.