Date: Thu, 15 May 2008 21:53:02 +0200 From: Volker Jahns <volker@thalreit.de> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-questions@freebsd.org, Volker Jahns <volker@thalreit.de> Subject: Re: time drift Message-ID: <20080515195302.GA13531@ikarus.thalreit> In-Reply-To: <597571FB-C72D-4603-B379-A59A435843BE@mac.com> References: <20080515185758.GA12709@ikarus.thalreit> <597571FB-C72D-4603-B379-A59A435843BE@mac.com>
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On Thu, May 15, 2008 at 12:18:57PM -0700, Chuck Swiger wrote: > On May 15, 2008, at 11:57 AM, Volker Jahns wrote: > >FreeBSD 6.2 running on X86 hardware (FSC) shows a remarkable time > >drift > > > >running ntpdate every half hour shows that the system looses about > >10-14 sec each time. > >15 May 10:06:48 ntpdate[7200]: step time server 192.53.103.108 > >offset -13.799602 sec > >15 May 10:36:48 ntpdate[7515]: step time server 192.53.103.108 > >offset -12.813941 sec > >15 May 11:06:48 ntpdate[7879]: step time server 192.53.103.108 > >offset -13.651921 sec > >15 May 11:36:50 ntpdate[8079]: step time server 192.53.103.108 > >offset -11.109298 sec > >15 May 12:06:50 ntpdate[8289]: step time server 192.53.103.108 > >offset -11.836499 sec > > While you should run ntpdate -b at system boot, running ntpdate > periodically via cron is not the right thing to do-- you should run > ntpd instead, and that will figure out the intrinsic correction your > chosen system clock needs to keep better time via the ntp.drift file. Running ntpd on this system results in time drift of approx. 1-2 hrs a day. That is not an acceptable option. > > You should also take a look at the output of "sysctl > kern.timecounter", and possibly switch to a different mechanism, if > the existing choice doesn't work out well for your machine... Thanks for the hint. -- Volker Jahns, volker@thalreit.de
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