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

Heiko Gerstung heiko.gerstung_removeme_ at meinberg.de
Tue Aug 1 10:46:51 UTC 2006

ter310 at gmail.com schrieb:
> 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:
[cut ntpq -p output]


Looking at the differences of the two billboards you sent us, your clock 
is really running fast ( 600 ms in two minutes? God heavens! ).

NTP will give up when it faces such a big problem, so your first goal is 
to get your system clock in a healthy state. Try it with a non-SMP 
kernel first in order to rule out the SMP kernel as a potential cause 
and it might be a good idea to contact the vendor of your server or 
mainboard and ask for help (BIOS update available?).

Best regards,

Meinberg radio clocks: 25 years of accurate time worldwide

MEINBERG Radio Clocks

Stand alone ntp time servers and radio clocks based on GPS, DCF77 and 
IRIG. Rackmount and desktop versions and PCI slot cards.

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