Time Synchronizing Between Two Servers

[Chuck Swiger]

On May 4, 2007, at 9:10 AM, RW wrote:
> On Thu, 03 May 2007 11:07:34 -0400
> Chuck Swiger <cswiger at mac.com> wrote:
>> Sun SPARC machines have good HW clocks, and also some of the newer
>> Macs also seem to have consistently low values in ntp.drift and
>> handle timekeeping well.
>
> Does that matter?

A good question-- the answer seems to be that it depends.

> The RTC time is almost immediately overridden by ntpdate. The
> drift is a systematic error that ntpd allows for. I would
> have thought that the only significant issue, is whether the system
> loses timer interrupts under load.

There are limits to how rapidly ntpd will slew the clock via adjtime 
(); the smaller the intrinsic drift of the HW clock, the sooner any  
adjustment (beyond the initial stepping at system boot via ntpdate)  
will complete.  This only matters to stratum-2 and higher systems--  
anything with a primary reference clock (GPS/WWV/ACTS/etc) is going  
to sync to that and ignore the local HW clock entirely.

-- 
-Chuck