What OS are your hosts running? If it's Windows, millisecond, not
microsecond accuracy will be what you can get at best when syncing over
the network.
A mixture of linux flavours and solaris. For the linux hosts I have a
little more control over which version of ntpd I deploy. For the solaris
ones, the stock version is ancient, not sure I have much control over
that one but it could be raised if necessary.
I read that folk who want the best accuracy will run FreeBSD rather than
Linux, but also that recent versions of Linux may not be as bad. How much
the NTP version will affect the accuracy on such systems I don't know, nor
how well Solaris performs.
If you really need microsecond, I suspect you will be looking at a GPS
receiver or two at each site, and distributing the PPS (pulse per
second) signal to each host, and praying that the hosts have a serial
port connection!
Well that's the rub - some of them don't :) If nothing else it might
inform new hardware purchases though. Some of these sites vary in their
willingness to allow GPS antenas on roofs as well, joy.
Cheers,
Paul
My gut feeling is that without GPS, microsecond accuracy is out of reach,
and likely without a direct PPS connection to the box as well.
It may not apply here, but is the requirement at all realistic? Was it
dreamt up off the top of someone's head? What happens if you say that
(for example) 100 microseconds is the best you can get. It's not
high-energy physics or radio astronomy, is it?
Not sure I can help any further, except to point you to my "best" PC,
which is a dual-core Intel Atom box, doing nothing other than time
serving, connected to a roof-mounted GPS, running FreeBSD. It's in a
domestic, non-temperature controlled, environment.
http://www.satsignal.eu/mrtg/pixie_ntp.html
The zero line of the graph is at +20 microseconds, as MRTG doesn't plot
negative numbers. The long term drift on the "yearly" graph is an MRTG
issue. The "spike" of several microseconds you see on Wednesday is just
the heating coming on here. Windows systems do not do as well:
http://www.satsignal.eu/mrtg/performance_ntp.php
You were planning on temperature controlled rooms for these systems, I
suppose?
Cheers,
David
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