[VoiceOps] [External] Re: [External] Re: [External] NTP Question

[Mike Hammett]

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. 




----- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 



Midwest Internet Exchange 
http://www.midwest-ix.com 



----- 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. 

http://hf0002.uah.edu/sharex/chrome_nj0IR7SmQr.png 

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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