<div dir="ltr">Steve,<div><br></div><div style>Completely agreed that there would be a difference but the 700-800Mbps usage is pretty sustained. I don't think it is simply the averaging over the interval that is causing the huge discrepancy.</div>
<div style><br>I misspoke in the earlier email - it is running on 5 minutes in cron. However, I've been watching it today and it is taking significantly longer than 5 minutes to complete. So I believe this is a likely candidate - the interval is set 5 minutes but it is actually only completing a run once every 15-20 minutes. I'm going to try changing the interval to a much larger value tonight, dumping the RRDs and setting cron to a value that it is actually able to complete.</div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, May 15, 2013 at 3:12 PM, Steve Shipway <span dir="ltr"><<a href="mailto:s.shipway@auckland.ac.nz" target="_blank">s.shipway@auckland.ac.nz</a>></span> wrote:<br>
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<div style="direction:ltr;font-size:10pt;font-family:Tahoma"><div class="im">>(Cacti is running on 1 minute, MRTG is running on 10 minutes.)<br>
<br></div>
And here we have the explanation.<br>
<br>
If MRTG is only polling every 10min (and you have the wrong Interval in the cfg file and in your RRD file for this) then it will be, in effect, giving you a 10min average speed for the port.<br>
<br>
Cacti, on the other hand, is polling every 1min and so is giving you 1min averages.<br>
<br>
Therefore, the MRTG graph will be much more smoothed out and flatter, and Cacti's graph will be more spiky, showing higher peaks for bursts of traffic that are relevant in a 1min interval but not over a 10min interval. This is why you see much higher values
in Cacti. The same effect happens in MRTG if you compare the peaks on a 5min average graph (daily) and on the 2hour average graph (monthly).<br>
<br>
Consider this set of 1-minute interval data:<br>
<br>
10<br>
1<br>
1<br>
1<br>
1<br>
1<br>
1<br>
1<br>
1<br>
1<br>
<br>
This is a 10min sample; for MRTG it would see a total of 19, IE 1.9/min. Cacti, however, would see them all, and show a graph with a spike up to 10. Therefore, very different graphs.<br>
<br>
If you want them to match, you will need to change the MRTG Interval to 1 minute, recreate your RRD files, and poll every minute - and change your PHP graphing script to take account of the higher granularity of data available.<br>
<br>
Steve<span class="HOEnZb"><font color="#888888"><br>
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<div style="font-family:Tahoma;font-size:13px"><strong>Steve Shipway</strong></div>
<div style="font-family:Tahoma;font-size:13px">University of Auckland ITS</div>
<div style="font-family:Tahoma;font-size:13px"><em>UNIX Systems Design Lead</em></div>
<div style="font-family:Tahoma;font-size:13px"><a href="mailto:s.shipway@auckland.ac.nz" target="_blank">s.shipway@auckland.ac.nz</a></div>
<div style="font-family:Tahoma;font-size:13px">Ph: <a href="tel:%2B64%209%20373%207599%20ext%2086487" value="+6493737599" target="_blank">+64 9 373 7599 ext 86487</a></div>
<div class="gmail_extra"><em></em>Voice: <a href="tel:%28414%29%20810-6392" value="+14148106392" target="_blank">(414) 810-6392</a> </div>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br>- Simon Westlake<br>[ <a href="http://digitalgunfire.com">digitalgunfire.com</a> ]<br>AIM: ShirowDG<br>ICQ: 2227213<br>Voice: (414) 810-6392
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