| RE: [chrony-users] Questions about a statistics.log field |
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- To: "chrony-users@xxxxxxxxxxxxxxxxxxxx" <chrony-users@xxxxxxxxxxxxxxxxxxxx>
- Subject: RE: [chrony-users] Questions about a statistics.log field
- From: Frank Wayne <fwayne@xxxxxxxxxxxxxx>
- Date: Mon, 07 Dec 2020 19:28:39 +0000 (UTC)
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- Thread-topic: [chrony-users] Questions about a statistics.log field
That does help, though field 4 becomes a little more mysterious. Is there anywhere these calculations are documented, other than the source code? I'm curious, if there are several variables involved, how their variances are combined to determine the final deviation.
-----Original Message-----
From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
Sent: Monday, 07 December, 2020 03:02
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [chrony-users] Questions about a statistics.log field
On Thu, Dec 03, 2020 at 08:23:31PM +0000, Frank Wayne wrote:
> Field 4 of statistics.log is the "estimated standard deviation of the measurements from the source (in seconds)", whereas field 6 is the "estimated standard deviation of the offset estimate (in seconds)". Field 6 is apparently the local clock jitter relative to the source, but what is “the measurements from the source” in field 4? Is this an estimate of the source jitter? If so, relative to what?
chronyd keeps a number of measured offsets for each source. The field
4 is the stability of the measurements. That includes the local clock, network and server clock. The field 6 is the estimated stability of the final offset calculated from those measurements and which updates the clock.
The values come from linear regression: data points vs the intercept.
Does that help?
--
Miroslav Lichvar
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