On 2011-04-20, David Lord <[email protected]> wrote: > unruh wrote: >> On 2011-04-20, David Lord <[email protected]> wrote: >>> unruh wrote: >>>> On 2011-04-19, David Lord <[email protected]> wrote: >>>>> unruh wrote: >>>>>> On 2011-04-19, David Lord <[email protected]> wrote: >>> ..... >>> >>>>>>> When I first compared chrony with ntpd there was no contest >>>>>>> but more recent experiments with chrony had periods of >>>>>>> severe instability much worse than ntpd. >>>>>> More recent means what? What version of chrony? (there was a bug found >>>>>> in the past two weeks that was introduces a few months ago which did >>>>>> result in instability) >>>>> More recent than November 2009. >>>>> Probably between Dec 2009 and Jan 2010 and p4x2400c. >>>>> >>>>> chrony 1.23 >>>> OK well before that change. >>>> >>>>>>> P4X2666 with chrony >>>>>>> <http://www.lordynet.org.uk/mrtg/stats/> >>>>>> Not at all sure what I am supposed to see. I have no idea what the graph >>>>>> axes represent? What is 1.1k >>>>> X-axis is in hours >>>>> Y-axis is offset in us so 1.1k = 1100us >>>> WOW. What kind of network are you attached to? Even on an ADSL link >>>> through the phone company, I >>>> was getting in the tens of usec (not ms) as the offsets of chrony. >>>> (checked by a gps receiver attached to the local computer). >>> I'm on ADSL-1 with 2 Mbit/s down and 288 kbit/s up. Latency >>> is what BT delivers and has been as low as 12ms up to 50ms or >>> more but mostly it's about 18ms to nearest sites (when exchange >>> gets near capacity the latency jumps up by 15ms or more same as >>> when interleave is enabled on ADSSL-2). >>> >>> Although the peaks of the graph are at about 1ms the stats >>> have "System time" mostly being in the 10s of usec. >> >> Not sure what you mean by that. What I mean is , what are the measured >> offsets? (Of course if you have a GPS PPS that you could use as a >> reference-- not a source of time-- that would make much clearer what is >> going on.) > > My logs have eg: > Reference ID : me6000g > Stratum : 2 > Ref time (UTC) : Sat Jan 9 07:12:02 2010 > System time : 0.000001 seconds slow of NTP time
OK, that is the kind of thing chrony should do. Ie, to discipline the system clock to usec levels > Frequency : 0.125 ppm fast That is a really small drift rate. Just lucky I guess. > Residual freq : -0.010 ppm > Skew : 0.223 ppm So the frequency is really pretty stable. > Root delay : 0.001297 seconds > Root dispersion : 0.007492 seconds That is a huge root delay and dispersion. Where are your servers? > > > I've not yet checked all of the systems that were tried > with chrony but these servers are all in use so it's not > easy to just install chrony and expect it to work. Sure it is. Just install it, configure it and start it ( switching off ntpd first). Of course if your server is supposed to keep really good time all the time, then this might cause some initial problems as you switch over. > > > David > > > >> >>>> And what is it about the graph that makes you believe you are seeing >>>> instability. >>> There is nothing in that session but later graphs now >>> wrapped (as in loops around after a year) showed much >>> worse offset variations than the systems using ntpd at >>> which point I went back to using ntpd. >> >> Certainly not my experience. And the lack of evidence makes it hard to >> fix any problems if they are there. > > _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
