[mrtg] Re: RRDTool

[Thomas Brian Granier]

>It appears as if a value is being passed into the RRD database, but an
>inaccurate one. I picked one of my graphs for further analysis of the
>problem:
>
>MRTG version
>
>Current in: 467.5 kb/s
>Current out: 1206.1 kb/s
>
>RRD version
>
>Current in: 25.519 G
>Current Out 12.280 G

I've cross-referenced the value shown in one of my graphs to the value
shown for the interface in one of the routers I monitor. For this
particular case, this is what I noticed:

RRD Graph:

Current Out: 11.493 G
Current In: 3.947 G

Router statistics:
Outbound Bytes: 1436832346
Inbound Bytes: 493479377

If I multiply the Router Statistics by 8 to get bits I come up with the
following:

Outbound Bits: 11.495 G
Inbound Bits: 3.948 G

So it's pretty obvious to me that what's happening is MRTG is taking the
outbound/inbound bytes and passing it directly to RRD after multiplying
by 8 but before doing the difference between this one and the last one
and dividing by the time frame. This is fine, except RRD isn't doing the
work either apparently. I would have suspected that this math would have
either been done by MRTG or by 14all.cgi when it calls RRDTool to make
the graph.

Any thoughts?


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