[ntp:questions] ARRGH!!! I woke up to a 50 SECOND clock error.

unruh unruh at invalid.ca
Wed Mar 14 02:05:28 UTC 2012


On 2012-03-13, Ron Frazier (NTP) <timekeepingntplist at c3energy.com> wrote:
> Hi all,
>
> I just woke up to a 50 SECOND clock error.  Prior to the error, with my 
> PC locked into the GPS and the internet servers noselected, here's what 
> my peerstats looked like.  Baseline is the GPS.  Colored lines are 
> internet servers.

Did you shut down and restart your computer? Did you perchance do this
during the daylight savings time transition on a Windows system? Could
the error be related to the fact that Windows like time on localtime not
UTC?

>
> http://dl.dropbox.com/u/9879631/drifting01-peerstats.20120312.jpg
>
> Here is what was showing on the Meinberg Time Server Monitor when I woke up:
>
> http://dl.dropbox.com/u/9879631/drifting02a%20-%20insane.jpg
>
> And the graph of the peerstats for that time:
>
> http://dl.dropbox.com/u/9879631/drifting02b%20-%20peerstats%20insane.jpg
>
> The clock error was REAL, as confirmed by my atomic wrist watch.
>
> However, the loopstats graph for the same time period shows no problem 
> with the GPS:
>
> http://dl.dropbox.com/u/9879631/drifting02c%20-%20gps%20NOT%20insane.jpg
>
> So, I shut down NTPD and reset the time with a batch file that calls 
> ntpdate and querys the New York NIST server:
>
> http://dl.dropbox.com/u/9879631/drifting02d%20-%20set%20with%20ntpdate.jpg
>
> Here is the time server monitor shortly after NTPD restart:
>
> http://dl.dropbox.com/u/9879631/drifting02e%20-%20shortly%20after%20ntpd%20restart.jpg
>
> And after a 2nd restart:
>
> http://dl.dropbox.com/u/9879631/drifting02f%20-%202nd%20ntpd%20restart%20after%20insane.jpg
>
> And here are the current peerstats, which look normal.  The offset to 
> the internet servers tends to drift and will eventually cross the zero 
> line and get positive.
>
> http://dl.dropbox.com/u/9879631/drifting02g%20-%20peerstats%20after%20insane%20and%202nd%20reset.jpg
>
> The GPS appears to have been stable all through this, and was never 
> powered off or unplugged.  It looks like NTPD went crazy and reset my 
> clock for some reason.
>
> Here are the peerstats and loopstats during the insane period.
>
> http://dl.dropbox.com/u/9879631/loopstats.20120313-1-restart%20around%201350%20utc
> http://dl.dropbox.com/u/9879631/peerstats.20120313-1-insane
>
> Here is my current ntp.conf:
>
> http://dl.dropbox.com/u/9879631/ntp.conf
>
> My system is Windows 7, NTP 4.2.7p259, GPS GlobalSat BU-353 USB NMEA 
> only with GPGGA sentence at 57,600 baud.
>
> If anyone can shed some light on what happened, please do.  It's driving 
> me bonkers.  I don't believe the GPS is at fault, and I suspect NTPD.
>
> Thanks in advance.
>
> Sincerely,
>
> Ron
>
>



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