So why should you care about hypervisors vs. containers? Bottomley explains that hypervisors, such as Hyper-V, KVM, and Xen, all have one thing in common: “They’re based on emulating virtual hardware.” That means they’re fat in terms of system requirements.
Bottomley also sees hypervisors as ungainly and not terribly efficient. He compares them to a Dalek from Dr. Who. Yes, they’re good at “EXTERMINATE,” but earlier models could be flummoxed by a simple set of stairs and include way too much extra gear.
Containers, on the other hand, are based on shared operating systems. They are much skinner and more efficient than hypervisors. Instead of virtualizing hardware, containers rest on top of a single Linux instance. This means you can “leave behind the useless 99.9% VM junk, leaving you with a small, neat capsule containing your application,” says Bottomley.