[Beowulf] Docker vs KVM paper by IBM

[Kilian Cavalotti]

Hi all,

On Tue, Aug 19, 2014 at 7:10 AM, Douglas Eadline <deadline at eadline.org> wrote:
> I ran across this interesting paper by IBM:
>   An Updated Performance Comparison of Virtual Machines and Linux Containers

It's an interesting paper, but I kind of feel it's comparing apple to
oranges. They're both round and tasty, but it's not really the same
thing.

There's probably no need to detail this, but KVM is a virtualization
infrastructure that run full stack OSes (using their own kernels) on
top of a Linux kernel turned into an hypervisor. So yes, it carries
the overhead of running a kernel over a kernel, but also the
flexibility of doing so (ie. you can run different kernel/OS versions
on top of each other, use virtual devices and so on).
Docker, on the other hand, is a containerization infrastructure that
run processes on top of an existing, regular kernel. Not to diminish
its merits, which are great in many areas, but it's closer to a kind
of glorified chroot.

So, it's no surprise that Docker performance would be the same as the
underlying OS's, while KVM overhead is much more important. There's a
full layer of virtualization difference between the two.

And they also a ran single VM or container per host. It would probably
also be interesting to see what happens when your run multiple VMs or
multiple containers on the same host.

I guess it's nice somebody took the time to do the test, to ensure
that Docker management or the LXC infrastructure was not impacting the
containers performance too much, but I'm not sure I really understand
the goal of the paper. Worst case, it will probably be misleading for
people who will end up comparing two different tools with very
different purposes and use cases. "What do you mean I can not upgrade
the kernel in my container?"

Cheers,
-- 
Kilian