On Sun, May 13, 2012 at 9:00 AM, Hal Murray <[email protected]> wrote: > I don't think the pool command is very useful in the stable release. It's > been totally re-written in the last year or so.
The new pool implementation actually appeared early in the 4.2.7 series, in early 2010, along with the new DNS resolver useful after startup on which it depends. In 4.2.6 and earlier, "pool dns.name" would look up dns.name once at startup and configure as many server associations as there are IP addresses for the name, or maxclock, whichever is lower. With *.pool.ntp.org, each lookup yields 3 addresses so typically pre-4.2.7 pool will spin up three associations. It makes no difference if the servers in question are reachable or useful -- ntpd is stuck with them until restart. 4.2.7's pool command operates very much like manycastclient has for a long time. Additional servers are added when there are less than maxclock (default 10) associations active, including pool prototype associations. ntpd probes each IP address with a standard client query, adding associations for those which respond. >> But I don't see the point of more than 5, specially if ntpd tries to remove >> the bad servers itself. > > I don't think that ntpd currently removes "bad" servers. I think it dumps > servers that don't respond and then gets new ones. > > It seems like a good idea to do something like drop the worst server every > day or hour and see if you can find a better one. ntpd doesn't do that yet. I do see utility in configuring the new pool command using a default maxclock -- the excess allows ntpd to be smarter, particularly when minclock and/or minsane are raised appropriately. The new pool implementation, like manycastclient, does already have means to replace preemptable assocations which have not contributed to an offset estimation in 10 polling intervals. That protects those which show up with a tally code of * or +, leaving the rest subject to replacement over time. Cheers, Dave Hart _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
