Matthew Petach wrote: > > >> From: Mustafa <[email protected]> >> To: [email protected] >> Sent: Thu, December 24, 2009 11:45:03 AM >> Subject: [mrtg] MRTG exact sampling interval >> >> >> >> Dear all, >> Please I have a question, in the MRTG .log files >> there are 5 columns: >> 1- >> the first one is the time >> stamp in UTC >> 2- >> the second one is the average >> incoming transfer rate in bytes per second. This is valid for the time >> between >> the UTC of the current line and the UTC of the previous line >> 3- >> the third column is same as the >> second but outgoing. >> 4- >> The fourth column is the maximum >> incoming transfer rate in bytes per second for the current interval. This is >> calculated from all the updates which have occurred in the current interval. >> 5- >> The fifth is the same as the >> fourth one but outgoing. >> So that means that there is some sampling time that is less than the >> specified interval in the "mrtg.cfg" file to be able to detect the >> maximum. For example, I have adjusted the interval to be 5 minutes and I got >> values in the .log file as the following: >> 1251871200 124890 463933 204720 >> 497123 >> 1251864000 124836 >> 464014 188781 500925 >> 1251856800 153102 >> 478951 705564 892407 >> 1251849600 129210 >> 466166 185505 515786 >> As the second column is the average over 5 minutes, and the 4th >column >> values is much greater than maximum values, so my question is exactly: what >> is the minimum interval that the MRTG can detect >> a certain maximum throughput within it? >> > > The minimum interval is 5 minutes for detecting throughput. > > The section of the config file you have there shows data aggregated up into 2 > hour > intervals (note there are 7200 seconds between each line). Thus, column 2 is > showing > the average *over two hours*, while column 4 is showing *the highest 5 minute > value > recorded during that two hour interval*. That's why the numbers are so > different. > > If you look at the first 600 lines of the config file, you'll note those are > the 5 minute data > samples, and there, columns 2 and column 4 will be almost equal. As the data > gets > averaged more and more in subsequent sections of the file, the difference > between > the average and peak values generally gets larger. > > Hope this helps clarify what you're seeing. :) > > Matt > > >> Thanks a lot for your patience and your support, I really appreciate that. >> Best Regards, >> >> MUSTAFA A. ABDEL >> HADY >> Network Engineer >> >> >>
To further explain some of this, you are using MRTG in it's native logging form and not using rrd databases. Because of the way MRTG is programmed when using native logging and rateup, it does heavily depend on a 5 minute polling interval. You need to try to poll every 5 minutes to get accurate data and averaging from your devices. When you convert to rrd databases, you can poll more often and the front end(I recommend routers2.cgi) can be fine tuned. But the basis of all development was built around the 5 minute polling interval, so unless you have a real serious desire to poll more often, don't. And the cpu load in rrd mode is way less than using the native logging within MRTG. Lyle Giese LCR Computer Services, Inc.
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