[ntp:questions] Win7: ntpd adjusting time backwards
david at ex.djwhome.demon.invalid
Sat Dec 8 21:03:55 UTC 2012
Jeroen Mostert wrote:
> I thought ntp could adjust the time forwards in "big" steps, but would
> never adjust the time backwards. I'm guessing I got confused with the
> slew-only option (-x) for servers that absolutely cannot tolerate the
> clock going backwards, even if it takes forever to adjust it through
> slew only.
Even -x doesn't disable steps, it just requires a larger error (600ms)
before stepping. Also note that increasing the error before stepping
forces ntpd into a degraded mode where runs the discipline algorithm in
user space, every second, and runs the clock at +/- 500ppm for a
fraction of each second. In the normal mode, on suitable systems, the
kernel deals with the fine detail at the clock tick rate.
> With your explanation, I'm perfectly willing to blame crappy network
> conditions and/or crappy pool servers on the frequent adjustments.
> Looking at another machine, I see zero (0) adjustments there since ntpd
If you suffer from temporary severe asymmetric delays, you can use the
huff and puff tinker option to try and compensate.
> was configured to use a central, local time server (stratum 2). This
> machine has no time-critical services, so as long as it's accurate to
> within 1 sec/day I can't complain. I was just confused about the clock
> going backwards.
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