[ntp:questions] Why does ntp keep changing my conf file?
david at ex.djwhome.demon.invalid
Fri Sep 17 21:59:01 UTC 2010
Daniel Havey wrote:
> So, you think that a PC clock will drift 20-50ms in 5 seconds? Seems like a lot, but whatever. Let me see if I've got this right, you tell me I might get say synchronization of ~10ms with ntpd running on a lan with everybody on the same switch or perhaps one switch away?
On its own no. With the help of ntpdate, yes. I wouldn't actually
expect to reach this level very often, but I'd certainly expect several
milliseconds. You will get these large steps because you are using
individual measurements, which are very vulnerable to scheduling delays
and network propagation delays, which ntpd, itself, will average out (it
will effectively low pass filter the jitter out of the measurements).
If you seriously need very tight synchronisation, you should use ntpd or
possibly chrony, with a pulse per second source parallel wired to all
the machines. In extreme cases, you may need to make sure the
transmission lines from the PPS source are or equal length.
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