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

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Tue Mar 13 22:33:50 UTC 2012

On 3/13/2012 5:39 PM, David Lord wrote:
> Ron Frazier (NTP) wrote:
>> On 3/13/2012 2:40 PM, Chris Albertson wrote:
>>> On Tue, Mar 13, 2012 at 9:52 AM, 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
>>> Looks to me like that GPS, maybe lock lock and was able to "coast" on
>>> hold over for a while then fell off a cliff.     If you have a log of
>>> satellite  signal to noise ratios you might be able to figure out why.
>>> The internet servers appear to be 100% reliable seeing as they all 
>>> agree.
>>> These kinds of things are why some hobbysts end up buying multiple GPS
>>> (different brands)  Otherwise it is hard to sort out a GPS firmware
>>> bug from a solar storm or just that there were not sats visable to
>>> your indoor antenna for a few minutes
>>> I think your goal is to learn about all of this so these problems are
>>> a good thing.  No one learns much from working systems.   But if the
>>> goal is a reliable NTP server, the pool NTP servers can't be beat
>>> except by a good timing mode GPS, that has good self diagnostics and
>>> PPS.  The self diagnostics part is important
>> The link you quoted just now is not the one that bugs me so much 
>> today.  This one is the one that bugs me today, where my clock was 
>> stepped by 50 seconds for some reason.
>> http://dl.dropbox.com/u/9879631/drifting02b%20-%20peerstats%20insane.jpg
> I'm on a text mostly system so why do you require me to use
> a web browser to help you?
> What is your current ntp.conf, ntpd version, operating system
> and response of "ntpq -crv -p" after ntpd has had at least
> a day to stabilise?
> Not so long ago you posted that you had an offset within
> +/- 6 ms but didn't give any evidence. Response from
> "ntpq -crv -p" or better a day from peer_summary or couple
> of days from loop_summary would be enough.
> David
>> When I get the Sure board, I plan to hang it on the pc in tandem with 
>> this GPS and compare.
>> Sincerely,
>> Ron

Hi David L.,

I just figured the images and dropbox would be the fastest way to 
distribute the information.  I didn't think I could attach files to 
messages going to the NTP questions mailing list.

I'll be glad to provide stats files if anyone is interested.  Just tell 
me how to distribute them.

Based on advice from David Taylor, I just changed my configuration.  
Previously, I had only the GPS selectable and the internet servers 
noselected for testing purposes to try to determine where a slow 
drifting behavior is coming from.  Now, I have changed that so the GPS 
is noselected and the New York NIST server is the preferred and only 
selectable peer.  I am monitoring the GPS and other internet servers for 
comparison.  So, it will be a couple of days before this configuration 
accumulates some stats files.

Even though I have been tinkering with this GPS for a couple of months, 
I have never seen anything like the 50 second jump I started this thread 
about.  That problem may not be reproducible for some time, if at all.




(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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