[ntp:questions] Time steping regardless of "-x" slew only option

Richard B. Gilbert rgilbert88 at comcast.net
Sat Jun 23 21:59:21 UTC 2007

vwvr6vw wrote:
> I am using AIX 5.4 and NTP version 3.4 from what I can tell, which
> came with the operating system.  ntpq, "v" option returns 3.4y.
> This is not a startup condition.  xntpd has been running for a while
> before the steps.
> I realize that I have other issues causing the need for steps.  I am
> investigating this problem as well.  I only have one time server, so I
> have network issues or something that is causing the need for the
> steps.  Underneath the one server, we have several of our processors
> acting as servers to the rest of our system.  If one of our servers is
> having interrupt delays from disk activity or some other issue,
> perhaps that is causing the dicrepency.  Does anyone know the best way
> to debug such a situation?
> But I still need to understand why NTP is stepping when the
> documentation I have says that it should not with the "-x" option.  We
> have a distributed processing system with many processors.  It is
> imperative that time does not step on any of our processors or our
> software will detect heartbeat problems.  That is what is currently
> happening, so I know that real steps are occuring and not just steps
> in the ntp.log file.

Can you show us the output of "ntpq -p"?

It would also be helpful to see the contents of your ntp.conf.  Please 
omit the comments unless they are necessary for us to understand what 
your are doing.

The current version of ntpd (the "x" was dropped many years ago) is 
V4.2.x.  I think "x" was equal to 4 the last time I looked.  V3.4 is 
ancient!  Is it possible for you to upgrade to something a few years 
more recent?

Are the steps always in the same direction?  That is are they all 
positive, or all negative?  All steps in the positive direction would 
tend to suggest that something is masking or disabling clock interrupts 
for a much longer time than it should.  This problem is known to occur 
with some versions of Windows and Linux.  I have not heard of such a 
problem with AIX. . . .

As to why nptd is stepping, I can only guess.  If the local clock is in 
error by a significant amount, it could take ntpd a very long time to 
correct by slewing the clock.  The maximum slew  rate is 500 PPM or 
about 43 seconds per day.

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