[ntp:questions] Which version of Linux works best?

Chuck Swiger cswiger at mac.com
Wed Mar 10 17:32:21 UTC 2010


On Mar 10, 2010, at 7:25 AM, David J Taylor wrote:
> Yes, I know it's one of those low long is a piece of string questions, but I'm now considering a dual-core Intel Atom system, which is "Compatible with Linux" according the the very minimal blurb I have right now.  If the system is to be used purely for NTP with Linux as a serial-port GPS/PPS stratum-1 server (and, yes, I know dual-core isn't needed for that, but I might want to boot Windows-7 64-bit occasionally), and considering that I know very little about Linux, which version of Linux would the group recommend?  Does it make any difference as far as timekeeping is concerned?

The hardware you get matters much more than which OS or flavor of Linux you use; tweaking kernel compiler optimization flags matters even less.  It would be good to look into the hardware you get in terms of support for HPET, p-state invariant TSC, or how good the ACPI timers are.

> Two secondary questions:
> - how much better might FreeBSD be than Linux?  Any actual measurements?

There are some nice comparisons between different platforms here:

  http://www.dragonflybsd.org/presentations/nanosleep/

PHK, who wrote the FreeBSD timer code, is measuring ~150 ns timekeeping precision for a stratum-1 timesource:

  http://phk.freebsd.dk/soekris/pps/
  http://phk.freebsd.dk/pubs/timecounter.pdf

You might find some threads here interesting, also:

  http://unix.derkeiler.com/Mailing-Lists/FreeBSD/current/2005-10/1018.html

> - and one for Bill, how much better might chrony be than official NTP? Does it have a preferred Linux, or even freeBSD?

I gather that crony is intended for machines with infrequent network connections.  I can't imagine trying to run it for a permanently networked stratum-1 timesource.

> The system would /not/ be in a temperature controlled environment.

That's unfortunate; this effects your time stability more than any other factor being considered.  Well, try to make sure you get the PPS timesource working, as that will help.

Regards,
-- 
-Chuck




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