Miroslav, You are a wise man, sir! That is exactly what was happening.
I tried adding a new first server entry in ntp.conf -- for a non-existent IP on the same subnet. Whatever was going to sleep or timing out during the delay between polls got refreshed when ntpd tried to contact the first (non-existent) server. Now the delay and offset to the two NTP servers agree almost perfectly. I'll need to run this for several hours to be sure but it is probably good to a couple of microseconds or better.
Based on your suggestion, I have to conclude that the cause is probably more closely tied to Linux and/or PC hardware than it is ntpd.
Thanks for the idea! On Thu, Feb 25, 2016 at 02:49:48AM -0800, Weber wrote:
ntp.conf is specifies both servers with minpoll 4/maxpoll 4. Peer and loop statistics are enabled.
By just changing the order of servers in ntp.conf the delay and offset values in peerstats are swapped. Now it is A with 60us delay and B has 85us. Similarly, A's offset is not -5us and B is showing +5us. It appears there is something in ntpd where measurements on server A in ntp.conf come out slightly different depending its ordering in ntp.conf.
When A is specified as first in the config, the interval between polling of A and B will be 1 second and the interval between B and A will be 15 seconds. When you swap the servers, the intervals will be swapped too. I think there could be a lot of things than would happen in 15 seconds, but not in 1 second. Maybe some power saving feature is activated or maybe some cache entry expires. You could try adding B manually via ntpq -c config:, timing the command so that the polling is exactly between two polls of B, and see what happens with the delays. Or you could run ping against the servers to keep the link "up". The direction in which the offset changed suggests it's the processing of the server packet that has the extra delay. -- Miroslav Lichvar _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
