I have a small network of Windows XP (64 bit) running simulations, with
NTPv4 running on all the boxes and using a GPS-based timeserver on the
company network. The ping time to the server is 2 milliseconds from my
desk, but I'm seeing random time errors of order plus/minus 5 to 10
milliseconds, based on loopstats data.
This level of timesynch error is OK for the simulation, but still that's
a lot of error. I get far better on big UNIX boxes.
The question is if this level of error is reasonable, given the setup.
I know that timekeeping under Windows is not optimum, but cannot change
the OS, so the question is if I have gotten things as good as they can
be, or should I dig deeper. One thing that comes to mind is to raise
the priority of the NTP daemon to exceed that of the simulation
software.
Thanks in advance,
Joe Gwinn
Joe,
This is the performance I see:
http://www.satsignal.eu/mrtg/performance_ntp.php
The XP systems are:
Feenix: GPS-synched
Narvik: LAN-synced to Pixie (FreeBSD with GPS source)
Your best bet would be to add a GPS source to your Windows PC, when you
might expect errors of less than 250 microseconds under stable running
(i.e. leave the PC on 24 x 7). If you can't do that, PC Narvik suggests
you might get within +/- 1.5ms. That's with a configuration file like:
server A iburst maxpoll 5
server B iburst maxpoll 5
server C iburst maxpoll 5
where A, B and C all have a GPS source. All PCs on the same switch, so a
much better ping than 2ms. You could reduce the maxpoll further to 4 (if
the server operator agrees) and get somewhat better performance, and
keeping the PCs in a stable temperature environment would also be likely
to help. The bumps at 05:00 are when the heating comes on.
In my experience, changing the priority of NTP doesn't help a lot, but
most of my PCs are not CPU-bound. But I have given the account the rights
to do that.
Cheers,
David
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