| Re: [chrony-users] Polling intervals between peers |
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On Fri, Mar 01, 2019 at 09:33:54PM +0100, cfanygapa wrote:
> Thank you Bill, that was helpful.
> But from practical point of view, do you have any recomendations how to tune
> minpoll/maxpoll/polltarget ?
>
> The only thing I found is short paragraph from Chrony FAQ (https://chrony.tuxfamily.org/faq.html#_how_can_i_improve_the_accuracy_of_the_system_clock_with_ntp_sources)
>
> "Generally, if the |sourcestats| command usually reports a small number of
> samples retained for a source (e.g. fewer than 16), a shorter polling
> interval should be considered. If the number of samples is usually at the
> maximum of 64, a longer polling interval may work better."
That applies to the symmetric mode too. One important difference to
the client/server mode is that peers are normally using the same
polling interval between them (as long as it's between their
minpoll/maxpoll setting). So, if one peer has a significantly more
stable clock than the other, and it would prefer a longer polling
interval, it won't be able to use it because it has to poll evenly
with its peer.
As for NTP documentation recommending poll of 6 for best stability,
I'm not sure what was the reason behind that. I think in modern LANs,
a shorter interval would probably work better, even with ntpd.
--
Miroslav Lichvar
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