On 2013-04-17, David Taylor <[email protected]> wrote: > On 10/04/2013 03:07, Blair Zajac wrote: >> Thanks Charles, >> >> OK. So unless I go for some GPS-based clocks in my servers, each data >> center will use close stratum-2 servers and the stratum-3 clocks will >> not peer with clocks in my other datacenters. >> >> Regarding peering, then should each stratum-3 server in a single data >> center use all 4-7 upstream clocks? Or should the 4-7 be split between >> the three stratum-3 servers? The diagram at [1] suggests they should be >> split? If that's the case, then how are falsetickers identified? >> >> Blair >> >> [1] http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#AEN3101 > > That diagram (figure 5) shows each of the local prime servers being fed > from just two external sources, but as you say, 4-7 would be more > sensible. If it were me, I would go for one, two or three servers you > know you can trust being in common across the stratum-3 servers, and
Also make sure that those link back to different stratum 1 or 0 sources. It does little good to have 5 servers, all of whom derive their time from the same stratum 1 source, when that common source goes down. (ntpq -p tells you the source (refid) of the source you are using, and you can follow that back). Of course now adays, almost all refer back to a source that is GPS. So even if they have different gps receivers they are all back to a common source, the gps system. But perhaps if the whole gps goes down, or goes bad, we as a society will have bigger problems than our computer clocks. > fill in the rest with the "pool" directive. This will fill up the > servers with up to 10 external sources, which are dropped and an > alternative automatically selected if the source goes bad. > > I have information on my Web page about low-cost stratum-1 servers using > Windows, FreeBSD and Raspberry Pi PCs. > > http://www.satsignal.eu/ntp/index.html _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
