Richard Laager via devel writes: > The default for maxclock is 10. This includes the "pool" entries, of > which the stock Debian configuration has four: > pool 0.debian.pool.ntp.org iburst > pool 1.debian.pool.ntp.org iburst > pool 2.debian.pool.ntp.org iburst > pool 3.debian.pool.ntp.org iburst > > As a result, the default is to use 6 pool servers.
That is a cargo-culted configuration from an earlier (buggy) pool implementation in NTP classic that didn't mobilize enough pool servers when only a single pool line was present. With recent NTPd you really only need one pool ine and (especially if you have multiple server lines as well) a modified tos setup so that the selection algorithm does not kill all of them. Here's what I currently use: tos minsane 7 minclock 15 maxclock 35 ceiling 4 I have around ten fixed servers (most of them internal), so that setup leaves me with 5 internal and 10 external (mostly from the pool) candiodate servers when locked to the GPS refclock. The pool statement initially provides about twice as many servers as the surviving set finally contains and it does continue to weed out bad clocks and mobilize new ones if necessary (doesn't happen often, but it's nice to see that it works). > If that's true, then it seems like odd numbers of servers are better, > all things being equal. From there, it seems like I should set maxclock > to either 11 (so 11-4 = 7 servers) or 9 (so 9-4 = 5 servers). Any flaws > in this logic? No, at least if all your servers come from the pool. If not, the selection algorithm will prefer closer clocks with lower stratum (those on the LAN with their own refclock) anyway. Failover from a single local server going away is much smoother if you have at least five of them, I'd think that this should hold for pool-only setups. > Any thoughts on whether 7 servers or 5 servers is better? The same page > says, "Conventional wisdom is that using at least five upstream time > servers would probably be a good idea, and you may want more." The > conservative choice is 7, but is that likely to make a meaningful > difference compared to 5? Depends on how uniform the routing is across your pool. But I'd personally go for more than five, that makes it much more unlikely to get dealt an initial set that is off in the same way and thus looks good to NTP while it actually isn't. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ SD adaptation for Waldorf rackAttack V1.04R1: http://Synth.Stromeko.net/Downloads.html#WaldorfSDada _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel