[mrtg] Re: Smoother Graphs

[alex at ergens.op.Het.Net]

Matt Heckaman wrote:

> On Sat, 27 May 2000 alex at ergens.op.Het.Net wrote:
> [...]
> : If I understand your question, you don't want to graph the 5-minute
> : average but rather an average that is calculated over a longer period.
> 
> I took the question as more of a "if you get a 5 minute 2Mb/s spike when
> your average traffic load is say, 200-300 kbps, it screws up the graph
> until you go 24 hours without a peak." Now, by "screws" up the graph I
> simply mean that it shows the 2Mb/s spike which resets the scale of the
> graph thus making the 200-300 kbps average look like a tiny line on the
> bottom of the graph. At least, I think that is what he meant :)

I don't argue with you about that graph being hard to read.  However,
the question was about smoothening the graph.  This is IMHO the same as
spreading that 2Mbps spike (which for instance lasts 5 minutes) out over
(f.i.) 30 minutes.

In numbers:

normal rate 300kbps (during every 300 seconds)            ->  90,000kb
increase during 300 seconds:  2000kpbs-300kbps = 1700kbps -> 510,000kb
In the graph you see 5 periods with rate 300k and 1 period with rate 2,000k

after smoothening:
90,000kb+510,000kb=600,000kb in 1800 seconds
In the graph you see 6 periods with an equal rate of 333k
This way you are led to believe there is no problem with your bandwidth.

The correct thing to do if you want to see the lower regions without
loosing precision is either to hack rateup (make it display at most
400k) or convert to RRDtool (and write an appropriate script for it
that also limits the visible rate to 400k).
 
regards,
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