| Re: [chrony-users] chrony switch to low stratum very slow |
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On Wed, Aug 07, 2019 at 12:02:50PM -0700, chuang213 wrote:
> 2019-08-07 00:38:35 172.19.40.23 2 -14.307 0.054
> -6.028e-06 N 5 2.563e-05 7.701e-06 2.349e-04 1.930e-05 2.297e-04
> 2019-08-07 01:10:33 192.168.10.9 3 -14.307 0.000
> -3.306e-04 N 3 2.376e-04 7.130e-09 4.031e-04 3.629e-05 2.183e-03
> it seemed it took 16 seconds (the poll period) to switch server from
> stratum 3 to stratum 2. However, it took almost 32 minute, or 1918
> seconds to switch server from stratum 3 to stratum 2.
To me that looks about right. The second source not only has a higher
stratum, but it has also has a larger root delay and dispersion. With
the default stratumweight and reselectdist, the lower stratum source
has to gain about 1300 milliseconds to be comparable to the other
source, and if the dispersion rate is at 1 ppm (maxclockerror), it
will take more than 1300 seconds for the scales to switch in favor of
the other source.
You can set stratumweight and reselectdist to 0, but there will still
be some delay due to the increase in root delay and dispersion, and
the reselect process itself.
> Although I know lower stratum server is in favor but when it is
> unreachable, it should switch to other reachable server, sometimes
> lower stratum.
chronyd doesn't care about reachability very much. An old accurate
source that tracked very well may still be preferred over less
accurate/stable sources.
--
Miroslav Lichvar
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