[Fwd: Re: [ntp:questions] Re: drifting on crystal]

Richard B. Gilbert rgilbert88 at comcast.net
Fri Jan 14 16:46:00 UTC 2005

Marc Brett wrote:

>On Thu, 13 Jan 2005 23:39:24 -0500, "Richard B. Gilbert"
><rgilbert88 at comcast.net> wrote:
>>Alain wrote:
>>I believe that the presumption is that ntpd was restarted, either by 
>>itself or because the machine was rebooted.   In that case you don't 
>>really want the daily average as a starting value, you want the best 
>>available approximation to the correction for right now which would be 
>>the most recent recorded value.
>If it's true that drift values cycle over a period of one day, perhaps ntpd
>should be recording, say, 24 drift values, once every hour.  When ntpd is
>restarted, it could read the drift value which pertains to the current time of
>How much would this improve performance?  Confuse users?

It probably won't get done unless: a. you do it and, b. you convince the 
developers that it's a worthwhile improvement to put in the reference 
implementation.   In order to convince people that it was worthwhile, 
you would have to do some carefully documented testing that showed that 
the change made a significant improvement in startup/restart performance.

I'd question in just what circumstances such a change could be 
helpful.   Certainly it wouldn't be much help in a restart or reboot.   
The only circumstance I can imagine where it might help is following 
extended downtime.  Many causes of extended downtime would place the 
machine in an abnormal state in which any recorded drift value might be 

>Oh, and while we're at it, can we move the default location of ntp.drift out of
>/etc/ and into /var/ (or /var/something/)?  /etc/ is meant for configuration
>files, not rapidly changing stuff like clock drift.
AFAIK,  /etc is not a "default" location for the drift file.   You must 
specify the location of the drift file in your ntp.conf file.  If you 
don't specify a location, you don't get a drift file.   So go ahead and 
put it where you think it ought to be.   If there's anything at all, 
there may be a conventional location but no one is required to follow 
that convention.

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