But what could possibly cause rrdtool to interpolate wildly down? Is it somehow taking a U reading, considering it a zero, and interpolating with that? I would understand it if it took the old 1015.8 and the new 1012.8, and got something in between... a 1014 or something. But it doesn't do that! The "interpolated" number is outside the range of *any* previously seen datapoints, actually. Is this a bug? Or an undocumented feature? What is going on?
(a question of etiquette: should I be including all of the previous text from the ongoing thread, or just the bits I am responding to?) Al On Apr 27, 2011, at 4:11 AM, Jaime Lozano wrote: > Hello Aleksandr, > What you tell is very detailed. I don't know what is happening to your > graph. I don't know if this will help you. But remember that rrdtool > don't stores real data. I mean that maybe rrdtool is interpolating and > that's why the graph is not as exactly as you think it should be. > bye > > 2011/4/27 Aleksandr Pasechnik: >> Hello all! >> >> I have an rrd collecting meteorological data. It has a step of 300 seconds >> and data is fairly reliably entered every 150 seconds. There are times when >> my computer is off and no data is entered. Explicit U's would be entered if >> there was a problem getting the data, but I haven't encountered that yet. >> The strange thing is that I have been getting these big, unexplained jumps >> in the graphs (with corresponding strange numbers in the rrd dump) after >> blank periods. The parameter in question (it happens to the others >> sometimes, but for some reason this last time it only manifested in this >> one) is the atmospheric pressure. It is stored as a GAUGE with a heartbeat >> of 600, a min of 0 and a max of U. I've got some RRA's, namely Average, Min, >> and Max at xff 0.1, 1 data point, and 7340 rows (30 days of data i think); >> and xff 0.5, 12 data points, and 44040 rows (5 years of data). I'm currently >> plotting the last 24 hours of data with a resolution of one pixel per data >> point. Before the b lan >> k occurred, my script was writing 1015.8 into the pressure. Once the >> computer came back up, it was entering 1012.8 and 1012.4 (a bit of sensor >> noise between measurements i suppose). At no point did i write a 1008.9 or >> whatever its plotting there. Here is the offending graph output: >> >> http://russkey.tumblr.com/post/4971101013/jumping-rrdtool >> >> Any thoughts why this is happening? Anything I can do to stop it? I thought >> it might have something to do with the xff, so i changed it from 0.5 to 0.1 >> for the 1 data point per row RRA's but that doesn't seem to have helped. >> Though now that I think about it, perhaps it would make more sense to have >> just a single RRA for the 1 data point per row section, and have it a Last >> instead of an Average? Any help at all would be appreciated! >> >> Al >> _______________________________________________ >> rrd-users mailing list >> rrd-users@lists.oetiker.ch >> https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users >> > > _______________________________________________ > rrd-users mailing list > rrd-users@lists.oetiker.ch > https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users _______________________________________________ rrd-users mailing list rrd-users@lists.oetiker.ch https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
