[mrtg] Re: Max Rates reported by mrtg

Alex van den Bogaerdt alex at ergens.op.het.net
Wed Dec 4 14:32:20 MET 2002

On Tue, Dec 03, 2002 at 04:23:10PM -0500, John Graves wrote:

> Why is the weekly max rate (30 minute average) consistently larger  than 
> the Daily Max rate (5 minute average)?   This seems to be true even on a 
> fresh graph when there is not any historical data.

For the "daily" graph, MRTG uses averages and averages only.
For the "weekly" graph, MRTG can use (if desired) the maximum values.

avg_weekly = avg(avg_daily1,avg_daily2...avg_daily6)
max_weekly = max(max_daily1,max_daily2...max_daily6)

(where ..._daily1 means: 1st out of 6 intervals).

You never get to see max_daily1, except if you look in the log file.
The log file format is described in the documentation set, have a
look at it if you want.

How is it possible to get different avg_daily1 and max_daily1 ?

Suppose you're not monitoring at 5 past the hour.  Suppose it is
at hh:06 (and hh:11, hh:16 and so on).  Normalization will happen.
(see the faq, which is, by the way, operational again)
If the calculated rate at hh:06 is 10,000 and the rate at hh:01 was
0 then the normalized rate at hh:05 will be:  1/5*0 + 4/5*10000.
The maximum will be 10,000.

Again, this max value of 10,000 will not be visible in the daily
graph but it will be visible in the weekly graph.


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