Re: [c-nsp] NTP Servers

[Jimmy Hess <mysidia () gmail com>]

On 7/1/12, PC <paul4004 () gmail com> wrote:
> If your application requires sub-5 second accuracy, (such as end of a
> banking day), then Windows NTP is unsuitable for the purpose.
Looks like CYA on Microsoft's part.

That i've seen,   Windows NTP in physical environments with a hardware
system clock not having issues consistently provides  accuracy  better
than  +/-  0.5 against the time source it's synced with,  but  in
virtual environments,  which have incompatibilities with high
sub-second RTC accuracy in the first place, neither Windows nor Unix
NTP services are able to provide that consistently  without much
tinkering.

If it's absolutely critical that you have   sub-5  second accuracy,
even Unix NTP is not to be considered good enough,     you need highly
accurate hardware time source,  something more accurate than the usual
system clock you find in a PC or server.  Unix NTP can only do so much
to correct  for a broken system clock;  although it does do a very
good job disciplining PC real-time clocks that consistently run a bit
too fast or too slow,  ultimately the
personal computer clocks can at times be unreliable....

If they were perfect, you wouldn't need time sync in the first place;
just set them once,
and correct the  annual  0.01 seconds worth of error  once a year....

--
-JH