[mrtg] Re: Followup to: WithPeak[_] not reporting anything

[alex at ergens.op.Het.Net]

Isaac Grover wrote:

> After modifying the config to report the peak values for week and
> month, mrtg gives me the following graph for the monthly value. 
> While the additional colors make it look more attractive, I must
> honestly say that I'm a bit confused.  I was under the impression
> that WithPeak would give me a horizontal line across the graph
> representing the peak values for that given time period, but it
> appears to be plotting the peak values over the other data.  What's
> going on?

When MRTG calculates an entry for the weekly graph (in the log file) it
takes 6 daily samples and averages them into one weekly sample.
It also keeps the highest daily sample seen in that period and calls it
the maximum.

So, if the 5-minute averages are:  10k 20k 30k 40k 10k 10k
the 30-minute average will be: 20k
the 30-minute maximum will be: 40k

You can use the averages to see what amount of data was transported.
The maximum should be used to look at the rate.

Suppose there is a line that is utilized fully during office hours
(09:00-17:00) and that this line is idle during the rest of the day.

On the daily graph you can see this with no problem.  It is easy to see
what's happening.

On the weekly graph it is still no problem.  The data is consolidated
into 30-minute time slots.

The first problems occur in the monthly graph.  The data is consolidated
in 2-hour time slots and the slot that goes from 08:00 'till 10:00 has
only half of the rate.  The time slots 10:00-12:00 'till 14:00-16:00 are
okay and the slot from 16:00-18:00 displays the half rate on average.

In the yearly graph all time slots are 24 hours wide.  This means that
the average rate will be one third (8/24) of the full line speed.


If you also display the maxima, these will show you a full utilization
of the line in every time slot that has 09:00-17:00 in it.  This means
no change for the weekly graph, another value in the monthly graph for
both 08:00-10:00 and 16:00-18:00 and another value on the yearly graph
for every weekday.

HTH
-- 
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 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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