[ntp:questions] serialPPS+gpsd+ntpd large offset & jitter

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Wed Jan 12 11:07:20 UTC 2011


Even if you have a perfect source of UTC, it's going to be hard to
keep a typical Linux server within 5 microseconds of that clock.

I think you need to reconsider the whole system.  Where
did that 5 microseconds come from?  What happens if/when
the clocks are off?

Can they be off occasionally, or does something nasty
(factory melts down) happen if they ever get out of sync?

What is the temperature like where the machines are located?

One of the major sources of clock inaccuracy on typical PCs
and servers is the minor change in frequency of the system
clock because the temperature of the crystal changed.

There are typically two sources of temperature change.
One is the environment, the temperature typically has
a sawtooth pattern as the air-conditioner turns on/off.
The other is internal heating.  The internal temperature
goes up when the CPU does work.

-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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