[ntp:questions] how long does it take ntpd to sync up

unruh unruh at wormhole.physics.ubc.ca
Sat Aug 27 19:36:02 UTC 2011


On 2011-08-27, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> On 8/27/2011 12:49 PM, C BlacK wrote:
>> I read somewhere that it takes an ntpd 24 hours to truly sync up to a stratum 2 master.
>>
>> Is this true?
>>
>> Thanks
>>
>> Chip
>
> It's nowhere near that bad!
>
>  From a cold start, it will take about thirty minutes to get a 
> reasonable approximation of the correct time.  NTPD will need about
> ten hours to achieve the maximum accuracy that it's capable of.  If
> you are serious about having the correct time, you run NTP 24x365.
>
> If you want to run from 9:00 AM to 5:00 PM *only*, NTP is a poor choice 
> for the job.  There is a tool called, I believe, CHRONY, which works 
> much faster.  You pay for the speed with somewhat reduced accuracy!

Actually, all my measurements indicate that you pay for the speed with
somewhat increased accuracy (like factors of 2 to 3-- actually factors
of 100 better accuracy than ntpd have been claimed with GPS refclocks)
> This is usually not a problem unless you care about the microseconds.




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