[ntp:questions] NTPD can take 10 hours to achieve stability

unruh unruh at wormhole.physics.ubc.ca
Tue Apr 19 20:31:44 UTC 2011


On 2011-04-19, David Lord <snews at lordynet.org> wrote:
> David J Taylor wrote:
>> "unruh" <unruh at wormhole.physics.ubc.ca> wrote in message 
>> news:slrniqpa40.ppu.unruh at wormhole.physics.ubc.ca...
>> []
>>> Well, I think someone other than the current maintainers will have to
>>> port it to windows. Since windows timekeeping is not the worlds best
>>> anyway, it is probably true that the extra accuracy of chrony is
>>> unnecessary. It does have a command line option "like ntpq -p"
>>> provided by chronyc (depending on what you mean by "like").
>>> What MRTG is I do not know.
>>>
>>> If you are happy with ntpd, by allmeans stay with it.
>> 
>> A pity that chrony will not be offered for Windows, at least for tests 
>> to see whether it lives up to its claims.  There are times when a more 
>> rapid convergence would be welcome, such as the reboot of PC Molde 
>> around 13:30 yesterday:
>> 
>>  http://www.satsignal.eu/mrtg/molde_ntp-b.html
>> 
>> MRTG is a standard logging tool for network I/O which uses SNMP to 
>> produce the graphs I have quoted here many times for network throughput 
>> and timekeeping:
>> 
>>  http://www.satsignal.eu/mrtg/performance_network.php
>>  http://www.satsignal.eu/mrtg/performance_ntp.php
>> 
>> I've written how to extend MRTG to monitor NTP timekeeping, and various 
>> other parameters such as disk space and temperature here:
>> 
>>  http://www.satsignal.eu/ntp/NTPandMRTG.html
>>  http://www.satsignal.eu/mrtg/performance_howto.php
>> 
>>  From chronyc I would need to be able to use a simple Perl script to 
>> extract the numbers to be plotted - such as the Offset in the graphs 
>> above.  An easy job if the format is standardised and machine readable.
>
> I based my script on yours for ntp but changed from using a
> linear axis to log. I first used chrony on NetBSD when on
> dialup with demon and later for a while when on broadband.
> When I first compared chrony with ntpd there was no contest
> but more recent experiments with chrony had periods of
> severe instability much worse than ntpd.

More recent means what? What version of chrony? (there was a bug found
in the past two weeks that was introduces a few months ago which did
result in instability) 
>
> P4X2666 with chrony
><http://www.lordynet.org.uk/mrtg/stats/>

Not at all sure what I am supposed to see. I have no idea what the graph
axes represent?  What is 1.1k ?

Note that you can see my offsets with chrony on my web page. The network
problems really do cause difficulty, but the offsets in general are very
small -- 10usec over the network. 



>
> Current stats all with ntpd.
><http://www.lordynet.org.uk/mrtg/stats/ntp/>
>
>
> David
>




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