[ntp:questions] NTP - best practice if there is a local stratum 2 server

Rob nomail at example.com
Sun Jun 28 18:01:23 UTC 2009

Dave <foo at coo.com> wrote:
> I assume, for absolute accuracy (which is not important here, but I'm 
> intersted), this is going to be better than any attempt to set the time 
> from the ntp pool. Is that correct?

You never know that.
What you get from the pool may be a stratum-1 server locked to GPS time
on a fast unloaded connection, or it may be a slow box on a saturated
ADSL line and synchronized to time.windows.com.

Your local server will be better to depend on.  You at least know what
you get, and/or you can ask the department it belongs to what quality
you can expect.  You can never do that with the pool.

> But setting the time from the local server is also going to be cause a 
> problem if that server fails for some reason.


> Is there any way to make use of a local server if it's working, and then 
> use the pool if its not?

Of course.  When you configure the local server as a "prefer" server, it
will usually work out that way.

> To be honest, this is all a bit academic, as there is no real practical 
> need to have an accuracy of better than a minute or two on these 
> machines. In fact, an hour wrong would not make much difference but it 
> might irritate a few people.
> But it is important the two machine agree with each other, as otherwise 
> files appear to be created in the future by a few ms, which screws up 
> the 'make' program some times.

Then you should, as you do, synchronize one to the other or both of them
to the same (local) third server.

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