[rrd-users] Consolidation Happening even through I don't want it to!!

O'Neil, Donald A. DONALD.A.O'NEIL at saic.com
Tue Apr 14 18:02:33 CEST 2009

I've been running Cacti for quite some time now, and used RRDTool v1.2.15 all the way through 1.3.7, which is what we're currently using with Cacti.

When I setup up RRA files that have NO consolidation, I'm still seeming to get consolidation in the graphs. It may not actually be getting consolidated, but maybe it's the way the graphing algorithms 'squish' 8900 rows into a 500 pixel wide graph...

In any case, what is happening is the average, min and max numbers are not being represented correctly in the graph, or in its legend block.

This is what RRDTool graphs: http://www.lizardhill.com/cacti/graphexport.png 

This is the actual average/max when you analyze the CSV dump:

Traffic In PEAK [Bits/s] AVG [Bits/s]  
	     0.84 M        12.64 k 

Traffic Out PEAK [Bits/s] AVG [Bits/s]
            1.53 M        11.61 k

Here is a CSV Dump of the above graph from Cacti... which shows the correct info as per the table above: http://www.lizardhill.com/cacti/dataexport.zip 

I'm thinking there could be 1 of 2 things going on... cacti isn't calling RRDTool correctly, so the graphs are being consolidated, or RRDTool is interpolating the data, and mis-calculating the actual peak/average, as well as graphing it incorrectly, maybe due to a simplistic approach to making the data 'fit'. I dig through all the cacti code and it appears to be sending all the raw data to RRDtool, otherwise I'd expect the export to not have all the data points.

If I plot the data in Excel, the graph represents the true data, with all the peaks preserved.

Any ideas where to look, if this is a cacti issue or an RRDTool issue?

Don O'Neil
Senior Network Engineer
SAIC - CCSD Network Operations
(702) 351-7261 cell
(702) 799-6174 fax
0099-5941 wan
oneilda at saic.com

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