[dns-operations] Docker

George Michaelson ggm at apnic.net
Sun Aug 7 23:47:08 UTC 2016

I too decided not to do a bunch of stuff (tcpdumps, timestamped packet
analysis) from virtuals because I worried about isochrony. Then I noticed
that even on bare metal, I could drop UDP in the kernel, get out of order
presentation up into the user process, not log the query in bind..

So I ran a job sending a million (queue image of evil person with pinkie to
lips)  queries and checked tcpdump order on bare metal and on a virtual. It
didn't seem to make any difference: the virtualized packet drivers these
days really don't represent more overhead on you than many other things
your kernel is doing.

I am unconvinced that for most of us, the distinction matters. I am sure
there are corner cases, but I think its very likely that time variance and
lossage from virtuals compared to bare metal _for most people_ is below the
noise threshold.

If you put the virtual on some platform which is flogged, and has
insufficient disk, memory, faulty VT logic I have no doubt this isn't true.
Equally, if you run bare metal on a Raspberry Pi, I suspect your not
getting the best response per packet.



PS maybe there's a student project lurking in this? If it turns out there
*is* a systematic variance by OS and {server type} and
{jail,dock,VM,Xen,bare-metal,Kubernetes} which exceeded the variance from
other sources, wouldn't it be nice to know?

On 7 August 2016 at 21:36, Phil Regnauld <regnauld at nsrc.org> wrote:

> sthaug at nethelp.no (sthaug) writes:
> >
> > Trying to avoid complexity and issues like the ones mentioned above is
> > why I run my name servers on bare metal. YMMV.
>         You can run Docker in a VM, or on bare metal (most do).
>         The *assumption* is that you'll be running containerized services
> on
>         RFC1918 nets and NAT on the host. It's a different approach to
> doing
>         things, but nothing forbids one from doing it their way.
>         If you want best of both worlds, and still do process isolation
> while
>         benefiting from "the full stack" and no network shenanigans, you
> could
>         be using FreeBSD jails or Linux' LXD.
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