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| Understanding the averages http://www.steveshipway.org/forum/viewtopic.php?f=2&t=8107 |
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| Author: | ChristianKrausse [ Wed May 22, 2013 12:40 am ] |
| Post subject: | Understanding the averages |
Hello, I use mrtg/rrd among others to display some printer usage. It was mainly a test but now i want to understand the displayed values. So the first question is the Value "Total over rolling last month:" about how many days is this value? Second question: how could I reverse calculte from "working day average" to get to the "Total over rolling last month:"? (because the value seems very low, only to aprove this...) Third: why is "Total over rolling last month:" not an integer? It could only count integer values of pages. (I know it has to do with how RRD stores the data but I could not explain why) |
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| Author: | stevesh [ Mon Jul 08, 2013 11:15 am ] |
| Post subject: | Re: Understanding the averages |
The rolling Last Month is always 30 days, as there is not currently any way in RRDTool to dynamically determine a calendar month (its in the RRDTool wishlist for v2.0 though!) The working day average is the average rate during the highlighted hours, the working day. You cannot extrapolate this to a full month as it omits data outside of working hours. Values for total might be very low if you have incomplete data as it does not extrapolate to fill in missing values. It is not an integer because of Data Normalisation; this is a feature of RRDTool and becomes more visible with low-value integer metrics. Your printed pages is being converted to an average pages-per-second within RRDtool and then summed up, which will cause rounding errors and non-integer values. You can add the 'integer' option to the MRTG config file, and the 'fixunit' extended option if you're using Routers2, which will help conceal this. If you tell RRDTool one page was printed today, this converts to a 1/300 page-per-sec in the 5min window IF you saved the data right on the 5min boundary. Otherwise, this will be shared over the two neighbouring boundaries... so on page printed at 11:59 will be treated as 0.2 pages printed in the 11:55-12:00 window, and 0.8 pages printed in the 12:00-12:05 window. This effect continues up and results in the fractions you see as the time windows get larger. See here: http://www.vandenbogaerdt.nl/rrdtool/process.php |
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| Author: | ChristianKrausse [ Wed Jul 10, 2013 2:10 am ] |
| Post subject: | Re: Understanding the averages |
Many thanks for the information! very nice of you |
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