[ntp:questions] NTPD can take 10 hours to achieve stability

David Lord snews at lordynet.org
Tue Apr 19 10:02:08 UTC 2011


David J Taylor wrote:
> "unruh" <unruh at wormhole.physics.ubc.ca> wrote in message 
> news:slrniqpa40.ppu.unruh at wormhole.physics.ubc.ca...
> []
>> Well, I think someone other than the current maintainers will have to
>> port it to windows. Since windows timekeeping is not the worlds best
>> anyway, it is probably true that the extra accuracy of chrony is
>> unnecessary. It does have a command line option "like ntpq -p"
>> provided by chronyc (depending on what you mean by "like").
>> What MRTG is I do not know.
>>
>> If you are happy with ntpd, by allmeans stay with it.
> 
> A pity that chrony will not be offered for Windows, at least for tests 
> to see whether it lives up to its claims.  There are times when a more 
> rapid convergence would be welcome, such as the reboot of PC Molde 
> around 13:30 yesterday:
> 
>  http://www.satsignal.eu/mrtg/molde_ntp-b.html
> 
> MRTG is a standard logging tool for network I/O which uses SNMP to 
> produce the graphs I have quoted here many times for network throughput 
> and timekeeping:
> 
>  http://www.satsignal.eu/mrtg/performance_network.php
>  http://www.satsignal.eu/mrtg/performance_ntp.php
> 
> I've written how to extend MRTG to monitor NTP timekeeping, and various 
> other parameters such as disk space and temperature here:
> 
>  http://www.satsignal.eu/ntp/NTPandMRTG.html
>  http://www.satsignal.eu/mrtg/performance_howto.php
> 
>  From chronyc I would need to be able to use a simple Perl script to 
> extract the numbers to be plotted - such as the Offset in the graphs 
> above.  An easy job if the format is standardised and machine readable.

I based my script on yours for ntp but changed from using a
linear axis to log. I first used chrony on NetBSD when on
dialup with demon and later for a while when on broadband.
When I first compared chrony with ntpd there was no contest
but more recent experiments with chrony had periods of
severe instability much worse than ntpd.

P4X2666 with chrony
<http://www.lordynet.org.uk/mrtg/stats/>

Current stats all with ntpd.
<http://www.lordynet.org.uk/mrtg/stats/ntp/>


David




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