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

Bill Unruh unruh at physics.ubc.ca
Mon Jan 28 15:36:51 UTC 2008


What was the problem?

On Mon, 28 Jan 2008, Danny Mayer wrote:

> Unruh wrote:
>>  mayer at ntp.isc.org (Danny Mayer) writes:
>> 
>> >  David L. Mills wrote:
>> > >  Danny,
>> > > 
>> > >  It doesn't stop working; it just clamps whatever it gets to +-500 PPM 
>> > >  as appropriate. If the intrinsic error is greater than 500 PPM, the 
>> > >  loop will do what it can with the residual it can't correct showing as 
>> > >  a systematic time ofset.
>> > > 
>> > >  Dave
>> > >
>> 
>> >  I didn't mean to suggest that ntpd stopped running. It was that the 
>> >  clock was drifting steadily off into the sunset. I realize that if the 
>> >  problem corrected itself ntpd would bring things back to normal.
>>
>>  But that suggests that the drift rate of your chip became bigger than
>>  500PPM, which is huge. Maybe something altered the tick size
>>  inappropriately. ntp should have hauled the offset back to zero -- just
>>  taking a longer time ( 100msec at 500PPM takes about 200 sec to
>>  eliminate--
>>  which is not that long.)
>> 
>
> No, it was something else entirely and not something that ntpd, chrony or any 
> other application could do anything about. It's fixed now.
>
> Danny
>

-- 
William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
UBC, Vancouver,BC  |   Program in Cosmology |     unruh at physics.ubc.ca
Canada V6T 1Z1     |      and Gravity       |  www.theory.physics.ubc.ca/



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