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Date:      Thu, 15 May 2008 15:36:02 -0700
From:      Chuck Swiger <cswiger@mac.com>
To:        Volker Jahns <volker@thalreit.de>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: time drift
Message-ID:  <08073D5A-7E00-4BF3-BAC8-21088EB513D8@mac.com>
In-Reply-To: <20080515195302.GA13531@ikarus.thalreit>
References:  <20080515185758.GA12709@ikarus.thalreit> <597571FB-C72D-4603-B379-A59A435843BE@mac.com> <20080515195302.GA13531@ikarus.thalreit>

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On May 15, 2008, at 12:53 PM, Volker Jahns wrote:
>> 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.

Something's probably wrong with your hardware clock or there is  
something else going on, if it is really drifting at ~ 5% from real  
time.  Sometimes replacing the battery on the motherboard fixes this.   
Does "vmstat -i" show exceptional interrupt load or anything like that?

>> 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.

Indeed, try using one of the other timesources and see whether that  
corrects the huge offsets you are reporting.

-- 
-Chuck




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