On 08/07/12 02:37 PM, Steve Shipway wrote: >> I created an RRD with "-s 60", so I think it should record a data point every >> minute? I then try to get the average value over the last ten minutes with >> "rrdtool fetch example.rrd AVERAGE -r 600 -s -600", but instead of one >> average >> value, it returns eleven values, each one minute apart > > You don't say what RRAs you have defined in your RRD. Although -s60 means a > step size of 60 and therefore sample (pdp) at interval 60s, what is actually > stored depends on your RRAs. > > Assuming you have defined an RRA with 1cdp=1pdp, then you will be storing > data at 60s intervals, too. You COULD create an RRA with 1cdp=10pdp, which > will store data at 10min averages (which is apparently what you want). > > Using FETCH will retrieve the data as stored in the RRA. If you do not have > a 10min RRA, or if your requested time period does not exactly match the > 10min RRA periods, then you will use the 1min RRA (and get 11 samples). > > This second case is important. If you ask for a start of 12:00 and an end of > 12:10, this actually covers 11 1-minute periods. A 1min RRA would cover > 12:00:00 - 12:09:59, so asking for and end of 12:10:00 means you've gone into > the next 'bucket'. The closest match would be 11 samples from the 1min RRA > rather than 2 samples from the 10min RRA so that's what you get. RRDtool will > use the closest match from the available RRAs that gives as much or more than > you ask for. > > Of course, if you've not created a 10min RRA then you're bound to get 1min > samples. > > If you instead use rrdtool XPORT then calculations can be performed, and you > can obtain 10min intervals even if you do not have a 10min RRA available. > > Hope this helps!
Fantastic, thank you very much for this help! I defined only one RRA and I intended it to store ten averages, one minute apart, or 1cdp=1pdp, like you say: RRA:AVERAGE:.5:1:10 Thank you for explaining why FETCH behaves the way it does when I ask for an average over the last ten minutes, and suggesting that I create a ten minute RRA. But is it possible to create an RRA with one ten minute average, updated every minute? i.e. I want the most recent average of 12:00-12:10, 12:01-12:11, 12:02-12:12, etc. and not the most recent average of 12:00-12:10, 12:10-12:20, 12:20-12:30, etc. _______________________________________________ rrd-users mailing list rrd-users@lists.oetiker.ch https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users