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

David J Taylor david-taylor at blueyonder.co.uk.invalid
Tue Apr 19 05:55:16 UTC 2011


> Thanks for all the great answers.  Now for a harder question, how does 
> the accuracy of the local clock source
> affect the accuracy of ntpd.
>
> Thanks
>
>
> Chip

Chip,

It also depends on the OS in use.  Even with a timekeeping GPS (better 
than a microsecond), Windows does not keep time as well as FreeBSD.

Compare FreeBSD: PC Pixie,  Windows: PCs  Feenix & Stamsund

  http://www.satsignal.eu/mrtg/performance_ntp.php

In my experience, even given an accurate source (e.g. a PC syncing to a 
FreeBSD stratum-1 server), the network performance may have a greater 
influence that the performance of the reference clock, especially if that 
network contains gigabit components, or off-site connections, wireless, 
ADSL etc.

If you want the best accuracy, ensure your PCs have a serial port, and 
pipe a pulse-per-second signal round your lab.  NTP works well with that.

Cheers,
David 




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