[ntp:questions] Large offset (>200 seconds) during system boot

Nottorf, Stefan Stefan.Nottorf at plath.de
Mon Nov 23 13:02:52 UTC 2009


Hello,
I encountered a somehow strange problem with ntpd after system boots.
We powered down a whole HP-Enclosure with HP-Blades, all running ntp
4.2.2p1 at 1.1570 (packaged with RedHat Enterprise Linux Server 5.1 64
bit). All of these Blades use ntp.confs like the following :

driftfile /var/lib/ntp/drift
server blade0 iburst version 4
peer blade1
peer blade2
peer blade3
peer blade4
peer blade5
peer blade6

The blades were running fine before the shut down, with 6 ms offset as
worst synchronization (measured against a Meinberg GPS 167 Radio Clock).
After completely shutting down the enclosure and rebooting the blades
showed an offset of 211000 ms (+- 1500 ms). ntpq -p showed that all
sources had (more ore less) the same offset.
After a restart of the ntp demon (via /etc/init.d/ntpd restart) -
without changing anything in the config file - everything worked fine
again...
This also happens if I shut down only a single blade.
1) Has anybody else encountered this behaviour?
2) Has anybody found a workaround (especially with this version of ntp)?
3) Is there a known problem, if many ntpdemons (~16) start at approx.
the same time?
4) Is there perhaps some well hidden "synchronization mechanism" by HP
that sets the time in advance (in this case to a time 211 s off...) ?

I might also wait for the release of ntp 4.2.6 if this would fix this
behaviour, but my customer is quite sensitive about being an "early
adopter" (regardless of how well tested the software is). 
My current "workaround" (if it can be called so) is restarting the ntpd
after the system has finished booting.
Best regards,
Stefan Nottorf
 



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