On Fri, 17 Feb 2006 10:45:54 +0100, Hermann Hastig wrote: > Hi, > > Johan Swenker wrote: > >> Last summer something similar happened to me. but it strongly depended on >> my configuration. So please tell us about your configuration (like >> operating system etc.) > > It's a plain Linux 2.4 kernel on a Linux from scratch system, nothing > extra that plays with the system's clock. The machine is located in a > fairly large datacenter and does not have any other clock source than > the three upstream servers from de.pool.ntp.org. > > So, I think I can say that the datacenter's network connection has > definitly been stable as is the case with the temperature (as Richard > guessed), and there's also no external clock that could mess things up > somehow. > > I've watched the clock the last days. The drift file stays at 9.642
Sounds wrong to me. Please check (using ls -l) the last time the drift file was written. My system, admittedly in a non-airconditioned room, changes the frequency (grep freq /var/log/daemon.log) by 0.1 ppm or even more. > while the offsets to the (new) servers move between 1 and 20 ms (except > one that keeps shifting stratum between 3 and 5 and shows offsets up to > 83 ms). > Seems pretty fine to me (I don't care if the clock's a second wrong or > not). Or am I wrong here? Seems pretty bad to me. Even when you don't care if the clock is a second worng or not, ntpd should be able to keep it synchronised with a few milliseconds. Otherwise, you _do_ have a problem. > > About that maxpoll setting: Of course the offset may grow larger the > longer the poll interval which in turn makes it more difficult to keep > the local time right. But doesn't ntpd automatically keep the poll > interval within limits that still allow to slew the clock, or does it > simply go up until maxpoll, whatever may happen? The poll interval is adjusted such that the jitter is low. I don't know about the details, I can tell you the effects. One of my systems had a GPS-receiver. It polls the configured internet servers with minpoll. It has to happen this frequently, to be a good match with the GPS-receiver. It also polls a system on my LAN. Even though this polling happens with maxpoll, jitter is better than 10 times as low as jitter from the internet servers. When I would disable the GPS-reciever, all polling will slowly grow to maxpoll. Depending on the quality of the configured servers. > > Kind regards, Hermann Regards, Johan _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
