[ntp:questions] Re: drift/offset

Richard B. Gilbert rgilbert88 at comcast.net
Thu Feb 3 13:38:26 UTC 2005


Folkert van Heusden wrote:

>Hi,
>
>If I look at the grap of the drift/offset of my ntp-server, everything
>seems to be rather jumpy:
>http://keetweej.vanheusden.com/ntp_graph.png
>
>The drift can be explained by a bad crystal on the motherboard, but the
>offset puzzles me: that server is connected to a DCF77 receiver! It is
>also syncing to some time-servers on the net.
>Might it be that I'm doing something wrong?
>
>
>Folkert van Heusden
>
>Op zoek naar een IT of Finance baan? Mail me voor de mogelijkheden!
>+------------------------------------------------------------------+
>|UNIX admin? Then give MultiTail (http://vanheusden.com/multitail/)|
>|a try, it brings monitoring logfiles to a different level! See    |
>|http://vanheusden.com/multitail/features.html for a feature list. |
>+------------------------------------------= www.unixsoftware.nl =-+
>Phone: +31-6-41278122, PGP-key: 1F28D8AE
>  
>
Your system is obviously performing poorly!  Whether you are doing 
something wrong or not is a question we can't answer without knowing 
exactly what you are doing.

Can you post your ntp.conf file?   Does your DCF77 receiver give you a 
PPS signal?  If so, are you using it?

Looking at the graph of your drift and offset measurements, I think I 
see correlation between the drift and the offset measurements.   If 
there is correlation, one could be cause and the other effect or both 
could be effects due to some other cause.

Since your drift measurements are being made with respect to your DCF77 
receiver and network servers the problem could be either the crystal 
oscillator or the time sources!    The offsets could be explained by 
"clock hopping"!

Was your system synchronized with the same source for the entire 
period?   What is your poll interval for that source?

Can you post the output of ntpq -p?

In short, we need a lot more information!!



More information about the questions mailing list