[ntp:questions] Second attempt at GPS-18 based NTP server

David Lord snews at lordynet.org
Fri Feb 3 01:25:41 UTC 2012

David Woolley wrote:
> David Lord wrote:
>> I've just added the "minpoll 4 maxpoll 4" back to my ntp.conf
>> as it could reduce the 30 usec offset blips I get when logs are
>> rotated.
> That's almost certainly totally the wrong thing to do.  If you have 
> short periods of increased interrupt latency or network latency, you 
> want a long poll interval so that the samples with the high offsets (and 
> delays) are ignored.
> Forcing a short interval will make ntpd track the temporary errors in 
> the time measurements.
> Offset is not a direct measure of the timekeeping error.

I already know that the system can't correct for temperature
changes, as with poll interval 10, and no PPS, the offset will
just carry on increasing until stepped or until the temperature
change is reversed. If the cause of these blips is down to
temperature I'd expect the shorter poll interval to be better.
I'll leave it at "4" for a couple of days then have another few
days with poll increased to "8".

The blips are nearly always present, 15u up to 40u.


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