On Thu, Aug 1, 2013 at 3:58 AM, James Patterson <[email protected]> wrote: > > Hello, > > I have two questions. > > 1. I have to use some ntpd servers which list themselves as time > sources. They list themselves as stratum 16 and with a jitter or 16000, > so I hope this means they are ignored - but does it? > i.e. we point at two ntp servers 1.1.1.1 and 2.2.2.2 and when I run ntpq > -p IP I see that both 1.1.1.1 and 2.2.2.2 are listed with a maximum > stratum and a huge jitter. > Is this a good idea, and will it cause a problem? Can you point me at > some documentation?
Do you mean the undisciplined local clock, fudged to a high stratum? (As described on http://doc.ntp.org/4.1.1/driver1.htm)? It's not that uncommon to see this used in the wild, though I tend to dislike it personally. Where it does make a lot of sense is in environments where you are serving time to a private LAN and it is more important that the clocks all agree with each other than that they align with reality. (Consider a cluster of database servers that don't agree on the time. Nothing good will come of that.) I tend to think that is only appropriate in private LANs, though. For public-facing servers, I'm of the opinion that if you don't have the correct time, you should not serve guesses. Let the client deal with it as a routine server failure, not by offering inaccurate time, even if at a higher stratum. (But that's just my unqualified opinion.) More to the point, http://www.pool.ntp.org/join/configuration.html recommends against using a local clock as a source. > 2. To determine the health of the ntp service on a server we parse the > output of ntpq -pn and look for large offsets. This doesn't make a lot > of sense to me since ntp will ignore crazy servers. What's the best way > of asking ntpd if it is receiving time from a good time source? I find "ntpq -crv" far more useful here. Look for "sync_ntp" in the top, and then, in the key/value pairs, you can sanity-check stratum, root dispersion, and, more directly, offset. I have Munin set up to plot some of this stuff on graphs. That said, I do that to satisfy my curiosity. My server in the pool does not have any active monitoring/alerting (a la Nagios). I just let the pool's monitoring remote me from the pool if things go awry. Kind regards, Matt _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
