Re: Time Synchronizing Between Two Servers

On May 4, 2007, at 9:10 AM, RW wrote:
On Thu, 03 May 2007 11:07:34 -0400
Chuck Swiger <cswiger@xxxxxxx> 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

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