I hadn't understood what means "stepping" ( applied when offset is greater than 128 ms ), infact I believed clock converged gradually to real time with for example (3 sec for minute) in like manner to slewing method. Now I understand that stepping set clock immediately to correct time (both forward and backward) while slewing permit to adjust gradually time at max 0.5 ms /sec rate (ONLY forward). is'tt OK ? I'm going to use ntpd -qg to synchronize my Linux DB "clients" because I think today machine clocks are enough accurate and I don't await significant offsets (between real time and local time) from first synchronization, my opinion is to not use service but a program which starts at specific intervals.
----Messaggio originale---- Da: [EMAIL PROTECTED] Data: 01/05/2007 15.10 A: <[email protected]> Ogg: Re: [ntp:questions] stepping and slewing On 2007-05-01, Riccardo Castellani <[EMAIL PROTECTED]> wrote: > According to www.ntp.org in stanard Linux o.s. (adjtime(2) - > http://www.ntp.org/ntpfaq/NTP-s-algo.htm#S-ALGO-BASIC) time adjusting > has rate of 0.5ms per second That's the _maximum_ slew rate. The actual slew rate depends on a number of factors. > to slew time but because do you speak about "maximum" rate of 0.5 > ms/sec. ? The maximum slew rate is 500ppm; this is the equivalent of half a millisecond per second or 43 seconds per day. > Does ntpd use always the same 0.5 as value or it's a variable > parameter ? 500ppm is the _maximum_ slew rate that most kernels can tolerate. The actual slew rate depends on a number of factors. > I'm confused because "Rob MacGregor" said about step method (128ms < > offset < 1000s) : 1000 seconds == the default panic threshold. ntpd will abort when it sees an offset greater than the panic threshold 128ms == the default step/slew threshold. ntpd will slew offsets below this threhold and will step offsets above this threshold >Stepping: Time changes in large units, quickly With "Step" method >(settimeofday), time is gradually changed with higher rate or time is >changes immediately to correct time. step == reset the clock to the correct time in _one_ instantaneous step. A stepped clock can "move backwards". slew == adjust the clock by speeding it up or slowing it down. A slewed clock never "moves backwards" > example for use step method : my local clock is 5:00 pm and real time > is 5:05 pm, Ntpd set immediately local clock to 5:05 pm or it corrects > time gradually ? Slewing the clock to correct a 5 minute offset will take 6.97 days at the maximum 500ppm slew rate. 5 minutes is greater than the default 128ms step/slew threshold. In this case ntpd will _step_ the clock. Could you please explain what problem you are trying to solve and why you feel you need to solve it with 'ntpd -gq'/ntpdate ? -- Steve Kostecke <[EMAIL PROTECTED]> NTP Public Services Project - http://ntp.isc.org/ _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions Naviga e telefona senza limiti con Tiscali Scopri le promozioni Tiscali adsl: navighi e telefoni senza canone Telecom http://abbonati.tiscali.it/adsl/ _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
