[ntp:questions] Re: Getting good NTP tracking

Eino-Ville Talvala quantumet at gmail.com
Wed Jun 28 20:36:15 UTC 2006


Richard B. Gilbert wrote:
> Charles Allen wrote:
> 
>> I've lost track of who's said what, but at some point the original
>> poster mentioned that the offset gets worse during the day.  To that I
>> ask a question: Are the server(s) more utilized during the day?  If
>> so, would the gurus consider lost interrupts a possibility?  Looks
>> like CENTos uses the 2.6.x kernels which some have mentioned had
>> trouble at least at some point in past.
>>
>> I mainly mention this because this has come up as a possibility
>> several times over the previous months, and I was wondering if there
>> is a way to diagnose this problem, either with NTP tools, or using
>> OS tools.
>>
> 
> Lost interrupts result in the local clock being slow with respect to the 
> server.  The server will fall behind, step in the positive direction, 
> fall behind again, step, etc.  This seems to be a problem mostly with 
> Linux systems that update the clock at frequencies greater than 100 Hz.
> Some systems can set the update frequency to 250 or 1000 Hz and those 
> that do so have been known to exhibit this problem.

Where would I check on the clock update frequency?

-----


Peer stats from yesterday:

peers.20060627
ident     cnt     mean     rms      max     delay     dist     disp
==========================================================================
A.A.A.A  133    0.604    2.726   11.346   99.133   69.698   11.311
B.B.B.B  134    1.486   14.164  137.654   67.729  250.569   11.178
C.C.C.C  123   32.648   34.108  176.643  119.703  264.385   19.212
D.D.D.D  131   -2.643   67.035  731.930    0.486   22.607   11.261
E.E.E.E  132   -0.432    1.872   17.620    3.671   37.519   11.287
F.F.F.F  140   -2.113    1.226    4.530    0.998  938.963   39.071

I'm not sure overall this is any better - however, the tracking with the 
peer F.F.F.F seems good - if it maintains track like this, I'll be 
satisfied.





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