[ntp:questions] Re: Server time wandering even with ntpd

Richard B. Gilbert rgilbert88 at comcast.net
Thu Apr 27 23:31:59 UTC 2006


Michael Weber wrote:
> Greetings!
> 
> I'm brand new to this list so if this isn't the correct place for this question, please flame gently.
> 
> I am running an Oracle database on two Dell 2650 servers.  I run a script that resets the clock every night because after 24 hours the clock can be as much as 45 seconds off.  I have 20 other servers, running lots of OS's with no problem.  It's just these two servers which are the only two of this model I have in house.
> 
> I am running ntpd during the day, but it doesn't seem to be able to correct for the time issue.  I run it with this command line:
>          ntpd -U ntp -p /var/run/ntpd.pid -g
> 
> I realize that it is probably a hardware thing, but we got what we paid for with the Dell servers.
> 
> Here are the config's on that server:
> 
> # cd /etc/ntp
> # ls -l
> total 8
> -rw-r--r--    1 ntp      ntp             9 Apr 26 06:01 drift
> -rw-------    1 ntp      ntp           266 Feb  3  2004 keys
> lrwxrwxrwx    1 root     root           11 Apr 24 09:39 ntp.conf -> ../ntp.conf
> -rw-r--r--    1 ntp      ntp             0 Feb  3  2004 step-tickers
> 
> 
> # cat drift
> -134.277
> 
> 
> # cat ntp.conf
> 
> server phone2.alliednational.com
> 
> driftfile /etc/ntp/drift
> 
> authenticate no
> 
> I am running a script every hour that shuts down ntpd, runs ntpdate against the in-house time server (phone2) and restarts ntpd again.  I grab the output of that script in a log file which I copied below:
> 
> Shutting down ntpd: [  OK  ]
> 26 Apr 05:01:00 ntpdate[26000]: adjust time server 10.1.128.2 offset 0.043594 sec
> Starting ntpd: [  OK  ]
> Shutting down ntpd: [  OK  ]
> 26 Apr 06:01:04 ntpdate[26207]: step time server 10.1.128.2 offset 3.162581 sec
> Starting ntpd: [  OK  ]
> Shutting down ntpd: [  OK  ]
> 26 Apr 07:01:01 ntpdate[26383]: step time server 10.1.128.2 offset 0.567207 sec
> Starting ntpd: [  OK  ]
> 
> 
> As you can see, the time sync is wandering all over the place.  Because this database is used for our employees timeclock, and it was getting as much as a minute off by the end of the day, I had to update the clock every hour or people would start to complain.  I was running the script every day, but it wasn't enough.
> 
> Any ideas how to keep ntpd more in control?  I would really like to see the clock stick with the time server like it does on all my other servers.  I run ntpdate every night on every box, and I usually get a few millisecond adjustment, except on these two servers.
> 
> Thanx!
> 
> -Michael
<garbage removed>


Starting and stopping ntpd is likely to be less than helpful.  It can 
take ntpd several hours to pull your clock into really tight 
synchronization and that is assuming that you are using a time source 
stable enough to allow ntpd to do so.

Your problem could be caused by one or more of a long list of potential 
causes.

The list looks like:
Poor quality time servers,
Poor connection to internet servers,
hardware problems with your Dell servers
software problems with:
	Linux,
	disk drivers disabling or masking interrupts,
	the version of ntpd (some versions still being distributed should have 
been moldering the the grave for the last eight or ten years!)

How about showing us the output of ntpq -p  for your Dell servers?
The output of ntpq -c version,
The version of Red Hat you are running.  (I deduced Red Hat)

Tell us about nights and weekends.  Do you leave ntpd running?  Is ntpd 
able to maintain stable time while the system is quiescent?

Can you run ntptime in a cron job once an hour?  Do the successive 
values of "offset", and "frequency" suggest anything?  Ideally the 
absolute value of frequency should be less than 50 PPM and should be 
stable  Ideally the value of "offset" should be zero but it seldom or 
never is zero. +/- 10 milliseconds is good for servers on the internet 
more than that suggests a problem.

Changing the server statement in ntp.conf to read:
server phone2.alliednational.com iburst
should help ntpd to start up a little faster.

Using a single server can be a problem.  Ntpd has no choice but to 
follow it, right or wrong.  If it's behaving like a drunken sailor, your 
Dell server's time might be absolutely anything!  If you can tell me 
that it's using a GPS reference clock I'm not too worried about it; if 
it's using a single server on the internet just eliminate the middle man.

Anyway, I could blather on all day.  Give us something to work with!!




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