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

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Wed Mar 14 13:46:59 UTC 2012


On 3/14/2012 3:03 AM, unruh wrote:
> 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.
>>
>> http://dl.dropbox.com/u/9879631/drifting01-peerstats.20120312.jpg
>>      
> Looking at this graph, I see that the nmea source was already difting
> before the sudden jump. It lost 30ms wrt the other servers in the 20
> hours beforehand. Then it went crazy for a while and jumped to 80 ms
> ahead. I agree that this does seem to be that gps device. Which one is
> it?
>
> But that jump is 120ms not 50 sec.
>
> I recently had a Garmin 18 go nuts-- giving massive amounts of noise.
>
>
>    

That's very interesting.  David Taylor also said he saw this NMEA 
wandering effect on the Garmin.  Did your Garmin recover?  And, is it 
based on a SIRF chipset?

In another thread, someone else with a BU-353 said he saw an "offset 
storm" like the one in my graph.

Sincerely,

Ron

>    
>> 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.
>>      
> It also reset all of the remote servers at the same time? Since it was
> an offset of your system with respect to the remote systems.
>    
>> 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.
>>      
> Again, the remote servers all agree. The GPS time does not (driving your
> system time) .
>
>
>    
>> Thanks in advance.
>>
>> Sincerely,
>>
>> Ron
>>
>>
>>      



-- 

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such.  I don't always see new messages very quickly.  If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT c3energy.com



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