[ntp:questions] NTP Pool rules vs. four-server advice

Michael Deutschmann michael at talamasca.ocis.net
Mon Dec 19 06:23:18 UTC 2005


I've noticed a conflict between the instructions on the NTP server Pool
project page and other NTP advice.

It is commonly advised here to configure ntpd either to slave to 1
server, or to track 4 or more.  The reason being that, when not slaving
blindly to one server, NTP's algorithms require 3 good servers, and if you
know all three will remain good, you may as well blindly track one.

In contrast, the NTP Pool directions explicitly say to use only 3 pool
servers when using the pool alone, and only 2 if you have a local
timeserver at your ISP.  Presumably this also means only 1 pool server if
you have 2 others, and no pool servers if you have three or more others.

The intersection of these two rules mean the only possible answer is to
use one pool server with no backup, or no pool servers at all.

This means that the [012].*.pool.ntp.org hostnames are of no legitimate
use.


At present, I have my border NTP server slaved to my ISP's timeserver.
But that computer went nuts as of last Friday (It's in an endless loop
cycle of about twenty minutes -- it keeps letting the offsets to it's
reference servers drift to -2.8s and then resetting itself.), so I'm
considering adding the pool as a fallback.  But following all the rules,
this is impossible.

---- Michael Deutschmann <michael at talamasca.ocis.net>




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