[ntp:questions] NTP vs chrony comparison (Was: oscillations in ntp clock synchronization)

Maarten Wiltink maarten at kittensandcats.net
Tue Jan 22 22:26:16 UTC 2008

"Unruh" <unruh-spam at physics.ubc.ca> wrote in message
news:aCqlj.12849$vp3.7702 at edtnps90...
> "David L. Mills" <mills at udel.edu> writes:

>> There are lots of ways to measure the loop transient response. The
>> easiest way is to set the clock some 50-100 ms off from some stable
>> source (not necessarily accurate) and watch the loop converge. The
>> response should cross zero in about 3000 s and overshoot about 6
>> percent
> 3000 s is a HUGE time. For people who switch on their computers daily,
> that means most of their time is spent with the computer unsynchronised
> to best accuracy. The timescale of chrony is far faster. (I am not a
> writer of chrony.I am a user who is trying to get the very best out of
> the timekeeping.)

But NTP is from a time when people didn't switch on their computers
daily. When NTP was young, dinosaurs walked the machine room and
_you_ did _not_ get to decide when the machine on the other end of
your terminal was rebooted.

NTP can, after weeks of training, teach a computer to keep time very,
very well. As a result, it's less optimised for the other end of the

Features like iburst and the drift file can get your clock synchronised
to within a few milliseconds in less than a minute. If you want better
than that, or you want it faster... don't turn your computer off.

Maarten Wiltink

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