[VoiceOps] [External] Re: [External] Re: [External] NTP Question
voiceops at ics-il.net
Mon Feb 17 17:26:52 EST 2020
I was looking to get a couple Pis and use them to feed the VMs, but we don't currently have many (any) places on our fiber plant to locate even a Pi GPS box. That'll change in the coming months, but that's not now.
BTW: It seems like it's about $50 per hat to add GPS to a Pi, so we're probably looking at $100/box... not that it's prohibitive then either.
Intelligent Computing Solutions
Midwest Internet Exchange
----- Original Message -----
From: "Hunter Fuller" <hf0002+nanog at uah.edu>
To: "Alex Balashov" <abalashov at evaristesys.com>
Cc: "VoiceOps" <voiceops at voiceops.org>
Sent: Monday, February 17, 2020 4:19:27 PM
Subject: Re: [VoiceOps] [External] Re: [External] Re: [External] NTP Question
I wouldn't call it incredibly oversubscribed, though we are getting a
little close on memory these days.
We would have pursued it more, but after reading that the general
wisdom was to not do it, we just stopped doing it, and things got
better, and I never thought about it again until now. :)
But I could see how it would be a problem in a fully virtualized
environment. Maybe a Raspberry Pi with an RTC module could be an
interesting low-cost/low-maintenance NTP box. Easy to have 4 of them
when they're $50 per box.
On Mon, Feb 17, 2020 at 4:15 PM Alex Balashov <abalashov at evaristesys.com> wrote:
> Interesting. I'm thinking there's something else off there. Perhaps the
> hypervisor is incredibly oversubscribed?
> On Mon, Feb 17, 2020 at 04:12:59PM -0600, Hunter Fuller wrote:
> > I wouldn't say we need it to be "really precise," but we do need it
> > within a couple of seconds, and on ESXi 6 we were seeing boxes as far
> > as 500ms off. It may not apply to all VM environments, so I guess it
> > could be worth testing. But it certainly scared me off. With physical
> > NTP servers we achieve within 10ms generally.
> > On Mon, Feb 17, 2020 at 4:09 PM Alex Balashov <abalashov at evaristesys.com> wrote:
> > >
> > > On Mon, Feb 17, 2020 at 04:00:25PM -0600, Hunter Fuller wrote:
> > >
> > > > On Mon, Feb 17, 2020 at 3:57 PM Mike Hammett <voiceops at ics-il.net>
> > > > wrote:
> > > > > Is having four VMs running NTP a ridiculous proposition (well, other
> > > > > than resources, which it'll consume very little)?
> > > >
> > > > Yes. NTP servers should never run in VMs.
> > >
> > > I don't know about that. The nature of virtualisation has changed
> > > greatly over the past decade; VMs have gone from being a kludgy and slow
> > > software-emulated environment to almost a first-class CPU guest, thanks
> > > to paravirtualisation and supporting CPU features.
> > >
> > > And NTP is specifically designed for latency in a rather general sense.
> > >
> > > If you're using NTP for any really precise timing calibration, that's
> > > the wrong vehicle, anyway.
> > >
> > > -- Alex
> > >
> > > --
> > > Alex Balashov | Principal | Evariste Systems LLC
> > >
> > > Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
> > > Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
> > > _______________________________________________
> > > VoiceOps mailing list
> > > VoiceOps at voiceops.org
> > > https://puck.nether.net/mailman/listinfo/voiceops
> Alex Balashov | Principal | Evariste Systems LLC
> Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
> Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
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> VoiceOps at voiceops.org
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