Re: [PLUG] q. about docker-engine overhead

[Rich Freeman <r-plug@thefreemanclan.net>]

On Mon, May 21, 2018 at 1:43 PM Ron Mansolino <rmsolino@gmail.com> wrote:

> How much overhead will a (mostly gratuitous) install of docker put on a
(mostly unused) VPS?


DIsclaimer: I'm not an expert in Docker specifically and while I use
containers on Linux quite a bit I don't use Docker.  However, I have a
pretty good understanding of how it works.

If no containers are running it won't consume anything but disk space (a
tiny bit for Docker, plus the size of any images you maintain - an image is
about the size of a lightweight distro).  I don't think docker involves any
kind of heavy daemon running 24x7.

If a container is running then I'd expect its memory use to only be
somewhat larger than the same software running directly on the host, and I
wouldn't expect any CPU/IO overhead.  The memory use will be a bit higher
than the same process running on the host because it won't share any
libraries with the host.

In general Linux containers are very efficient, because as far as Linux is
concerned ALL processes effectively run in containers.  Processes running
directly on the host are just basically running in a "default" container of
sorts.  It is no different from running a process in a chroot - there is
some isolation but in the end they're just processes.

Now, obviously running 12 daemons on one host (containerized or not) will
require more RAM on that host than if you ran them on 12 separate hosts.
There is no getting around that.

Overhead is nothing like a VM.

-- 
Rich
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