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

Unruh unruh-spam at physics.ubc.ca
Tue Jan 29 03:48:15 UTC 2008


"David L. Mills" <mills at udel.edu> writes:

>David,

>We can argue about the Hurst parameter, which can't be truly random-walk 
>as I have assumed, but the approximation is valid up to lag times of at 
>least a week. However, as I have been cautioned, these plots are really 
>sensitive to spectral lines due to nonuniform sampling. I was very 
>careful to avoid such things.

But the "lines" I am refering to are not artifacts, they are there because
of the way the computer is used. -- the temp fluctuations caused by people
running the machine daily, except on weekends. These are not part of any
"random walk" process. They are real jumps in the drift rate of the
machine, large jumps, and definitely not random.

>Dave

>David Malone wrote:

>> Unruh <unruh-spam at physics.ubc.ca> writes:
>> 
>> 
>>>weekends. Lots of power at 10^-5 Hz and harmonics, and .7 10^-8Hz.-- more
>>>than would be predicted by 1/f
>> 
>> 
>> 10^-5Hz is about once per day. I'm not sure what .7 10^8Hz is - it
>> seems to be about once every 4.5 years? I would have assumed you'd
>> get power around 10^-5Hz (daily), 10^-6 Hz (weekly) and maybe 3x10^-8
>> (yearly) based on a mix of enviromental factors (air conditioning/heating)
>> and usage?
>> 
>> 	David.




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