Greetings: Can someone offer some help or insight on how the MAX CF does it's thing at a more detailed level. I've listed below the pertinant info and my understandings of each where applicable:
My sample RRD has step of 60 seconds. It gets fed data in the neighborhood of 60 seconds (+- 2 sec). Heartbeat of 180 secs and is not missing any data in this example - no unknown datapoints. DS type is GAUGE RRA is set up with consolidation function CF = MAX steps = 5 (consolidated data point built from 5 primary data points (5 samples, ~= 5 minutes)). In a typical set of primary data fed at very close to 60 seconds: i.e.: 121 121 124 125 128 rrdtool fetch shows for that consolidated data point a value of 1027974000: 1.2648333333e+02 (rounded and graphed at 126) I get a graphed value of 126 (not the MAX of the set which was 128 in this case). I understand how an AVG CF needs to be interpolated to fit the exact time sequences of the actual primary datapoints in the rrd, but for MAX, how does rrd do the interpolation? How does it look at the set of data fed and come up with 126.483333? In the example above, is rrdtool assuming there is a linear decrease of the value between 128 and 125 during the times those 2 data were fed-in and determined that it was 126.4 at the exact time of the actual primary data point? That would have to put the 128 WAY early (30sec) and I'm pretty sure that's not happening. It seems to me that for the MAX consolodation, rrdtool should find the max value within the two actual datapoints and use them as is, with no interpolation since it is a MAX we (I) want. For simplicity, let say time itself just started and the rrd interval was between the 2 timestamps of 1000 and 1300; a 300 second interval. At time 1002 we add 121 (this was a "late" entry for previous interval) at 1059 we add 121 at 1122 we add 124 at 1179 we add 125 at 1240 we add 126 at 1301 we add 128 I assume rrd is fitting the 1301 value back to 1300 using some interpolation. But how exactly? Thanks very much for the time to help/explain. Scott -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://www.ee.ethz.ch/~slist/rrd-users WebAdmin http://www.ee.ethz.ch/~slist/lsg2.cgi
