On 2015-02-21, Paul <[email protected]> wrote: > On Sat, Feb 21, 2015 at 1:57 AM, William Unruh <[email protected]> wrote: >> >> On 2015-02-21, Paul <[email protected]> wrote: >> > On Fri, Feb 20, 2015 at 3:23 PM, William Unruh <[email protected]> wrote: >> > >> >> ??? how do assume that the chrony docs do not tell the truth? >> ^ you >> > > Okay, I'll assume (or pretend) that you mean "Why do I assume the Chrony > documentation is in error" and the answer is believing you. This is why I > suggest you stop paraphrasing and stop asking for paraphrasing. Provide > references to sources and stop doing original research.
I was asking with respect to a specific claim that was made ( and you have erased) and wondering what you meant by it. > > You said: "Lichvar did some tests with PPS and found that chrony > disciplined the clock much better than did ntpd (factors of over 10)" and > since NTPd can get to sub-microsecond your statement means Chrony is > getting at least O(10) nanoseconds. ??? No it does not mean that. I was reporting the results of his experiments. His experiments were NOT "What is the best that can be achieved" but "here are the results on the same hardware". > > The Chrony document says: "With a good reference clock the accuracy can > reach one microsecond." That is not wrong. It may be conservative, but is not wrong. (if you get one picosecond accuracy that is also 1 second accuracy). > > So one of you is wrong. Except it turns out you're both wrong. Miroslav > Lichvar says "If the clock is stable enough, they can perform similarly." > so the Chrony doc understates the performance and you overstate it > considering the current/recent state of the art. Again, I report experiments I ran. I got about a factor of 2-3 better. Same computer, same setup (local network server), same situation (computer in use with varying loads). > > And now some original research: I switched my most challenging *client* > (stratum 2 on a powerline network) from NTPd to Ntimed-client to Chrony. > NTPd had excursions in O(10) to O(100) microseconds, Ntimed-client managed > O(1) to O(10) microseconds and Chrony managed a reasonably consistent 1 > millisecond offset. I used stock conf files except Ntimed-client doesn't > use one. So points to Chrony for being more consistent. Well, then there is some difference. No idea what you did. Note that I have plots, for about 5 years now, of my machines offsets. I have neglected them for about the past 3 years. I used to have one machine running ntpd and the rest chrony. If you are only getting 1ms, something is wrong, either in your configuration or something. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
