[ntp:questions] Re: NTP High Jitter and Reject Condition

Tom ter310 at gmail.com
Tue Aug 1 14:29:16 UTC 2006


Richard,

I'm fairly certain your right.  Am going to log a call with the
motherboard company.  I have another server with the same MB so I'll
test that when I get back from travelling to see if the issue
duplicates.  Either way, it looks like a hardware replacement is in
order.  This server will be running transactions so an accurate date is
vital.

Thanks for the help.
Tom

Richard B. Gilbert wrote:
> ter310 at gmail.com wrote:
> > Hello all,
> >
> > I am completely stumped by an NTP problem that I am having on a server.
> >  I've googled and tried everything to no luck, am hoping that someone
> > here can provide some advice.  Here is the situation:
> >
> > I have a server running CentOS 4.3 2.6.9-34.0.2.ELsmp on a PDSMi
> > Supermicro motherboard with a Celeron D 3.06GHz processor.  Note, I'm
> > running an SMP kernel so that APIC can handle the interrupts properly.
> >
> > I have /etc/ntp.conf configured to the CentOS 4.3 defaults, which means
> > it is polling the 0-2.pool.ntp.org server pool.  Upon boot, everything
> > looks okay, but within a minute or two, the jitter sky rockets:
> >
> > [root at neon ~]# date
> > Tue Aug  1 05:30:09 EDT 2006
> > [root at neon ~]# ntpq -p
> >      remote           refid      st t when poll reach   delay   offset
> > jitter
> > ==============================================================================
> >  ouvaton.info    134.157.254.19   2 u   31   64    1   87.432  -164.78
> >  0.001
> >  bq.serverrack.n 65.111.164.223   3 u   30   64    1    0.636  -177.35
> >  0.001
> >  msb.significant 64.142.72.248    3 u   29   64    1    2.278  -166.81
> >  0.001
> >  LOCAL(0)        LOCAL(0)        10 l   28   64    1    0.000    0.000
> >  0.001
> > [root at neon ~]# date
> > Tue Aug  1 05:31:59 EDT 2006
> > [root at neon ~]# ntpq -p
> >      remote           refid      st t when poll reach   delay   offset
> > jitter
> > ==============================================================================
> >  ouvaton.info    134.157.254.19   2 u   12   64    7   87.308  -748.55
> > 578.177
> >  bq.serverrack.n 65.111.164.223   3 u   10   64    7    0.604  -752.02
> > 587.210
> >  msb.significant 64.142.72.248    3 u   10   64    7    1.921  -750.65
> > 582.576
> >  LOCAL(0)        LOCAL(0)        10 l   10   64    7    0.000    0.000
> >  0.001
> >
> > If I check the associations, they always show 'reject':
> >
> > [root at neon ~]# ntpq
> > ntpq> associations
> >
> > ind assID status  conf reach auth condition  last_event cnt
> > ===========================================================
> >   1 34972  9014   yes   yes  none    reject   reachable  1
> >   2 34973  9014   yes   yes  none    reject   reachable  1
> >   3 34974  9014   yes   yes  none    reject   reachable  1
> >   4 34975  9014   yes   yes  none    reject   reachable  1
> >
> > I'm just baffled to why this is occuring; within an hour it'll be >
> > 1000.  I have run ntpdate several times and set the hwlock to the
> > system time, but inevitably the system clock runs way too fast, gaining
> > several minutes per day.  Note, if I do not run NTP at all, the hwclock
> > stays perfect, but the system clock still speeds too fast.  So, I
> > cannot be sure if this is a HW problem, network problem, or
> > configuration issue.  I have tried adding noapic, nolapic, noacpi to
> > the kernel bootup to no avail.  I have tried to boot into a
> > uniprocessor kernel, same behavior.  The server is hosted at Equinix in
> > Ashburn, VA and the network appears okay:
> >
> > [root at neon ~]# mii-tool
> > eth0: negotiated 100baseTx-FD, link ok
> >
> > I have setup NTP logging, but really do not know enough about the
> > protocol to troubleshoot effectively.  I've also tried pointing at
> > other NTP servers and get the same behavior.  I do not currently have
> > iptables running (the server is not in production yet) so 123 UDP
> > traffic is going through, and the provider has verified that there is
> > nothing on their side blocking it.
> >
> > Any help at all would be appreciated.  I will be glad to supply log
> > files, trace files, anything to get this resolved.  Thanks so much.
> >
> > Best Regards,
> > Tom
> >
>
> It sounds as if your system clock has a frequency error greater than 500
> Parts Per Million (PPM).   500 PPM is the maximum error that ntpd can
> correct.  IF that error is exceeded, your choices are to have the
> hardware repaired, replace the hardware, or give up!




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