On 2012-01-10, Marco Marongiu <[email protected]> wrote: > Hi all > > So, we have a leap second at the end of June. Before then, I'd like to > secure that our time-sensitive applications (e.g., a well known database > from a well-known software and hardware vendor) won't crash as they did > in 2006. > > As far as I remember, in 2006 we found out that the system clock stepped > back one second, the database engine got mad, and crashed. Back then we > were using NTPv3 because xntpd on some Solaris host didn't know about v4. > > But it was 6 years ago, and things seem to have changed in the meanwhile :) > > I understand from "the NTP timescale and leap seconds" by Prof.Mills > that modern ntpd doesn't step back the clock but either "freezes" time > during the leap second, or it slightly increments it at each read until > the "real time" catches up. > > Did I get it correctly? > > If yes, then I would like to know: > > - how can I tell if the operating system will freeze/slowdown, or step > the clock? > > - how can I simulate a leap second, and see how the system reacts? > > My understanding is that we have the freeze/slowdown behaviour > implemented from ntpd version 4 [1], but I don't find anything more > specific in terms of ntpd and OSs versions. > > If you have detailed operating systems- and ntpd versions that are known > to work either way, could you please share? > > Thanks a lot > > Ciao > -- bronto > > [1] http://www.eecis.udel.edu/~mills/ntp/html/release.html
It sounds like your old system may not have had the leap second implimented. In that case ntp would suddenly find it was out by a second. It would then make a jump in time ( sine the threshold is .128 sec) which with the inserted second would make it jump backward in time by a second, which is what you saw happen. Or you could run chrony, which does not jump (well you can have it jump depending on the user selected threshold) but slews quickly. (that only works on Linux/bsd not windows) think you may be able to adjust that threshold in ntpd as well, and make it greater than 1 second. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
