[ntp:questions] Slow sychronization

David Lord snews at lordynet.org
Tue Aug 18 22:59:33 UTC 2009


Ray wrote:
> Hi All,
> 
> I am running a new version of the NTP daemon, version 4.2.4p6, on a Linux 
> machine with kenel version 2.6.27.
> 
> When I start the daemon, the peer information shows that all the peer have a 
> offset of about 30 milliseconds. This offset will increase to about 50 
> milliseconds after an hour. It might take many hour to days before the 
> offset comes down to a few milliseconds. I tried using 'iburst' on the peers 
> to see if this would speed things up, but it made no difference.

I've seen same on NetBSD and FreeBSD and took it as normal on
a fresh install with large swings in offset until a reasonable
value for drift has been obtained. If you're lucky, a new
kernel doesn't cause a significant change from existing
driftfile value and sync will be quite rapid. Other point
mentioned in the 500ppm thread is that if the drift value is
large not only will it take a long period to sync, it may also
not be possible at all for ntp to adjust to a reasonable offset
or worse the offset will become unstable and swing wildly.

Here, with a small value of drift, a few ppm, or maybe an
established driftfile with larger frequency offset (but < 50ppm),
I'd expect time offset to be within a few ms after a couple of
hours or so assuming delay from sources is reasonably steady.

"ntpdc -c loopinfo" gives following for my three servers:

pc:                k6-400     p4-2400    via-c3-600
ntpd version:      4.2.0-r    4.2.4p2    4.2.4p2
offset(ms):        -0.0018    0.000037   -0.000336
frequency(ppm):    -0.876     8.868      -49.225

offsets taken at 30min split into ranges <.1ms <.2ms <.5ms etc
95%range(ms):      <5         <5         <10


David

> 
> Are there any settings to speed up this process? Is the a problem with this 
> version of NTP?
> 
> Thanks,
> Ray
> --------------------- 
> 
> 




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