[rrd-users] Re: functionality question

Kempf, Reed rkempf at rightnow.com
Mon Sep 10 17:33:18 MEST 2001

thanks for the info, I guess I just want the best of both worlds.

To make the graph readable for longer time periods (weekly, monthly),
averages are the way to go.  I was just curious if it was possible to pull
out a min and max value from rrdtool for a certain time period and GPRINT it
below the graph.

I have it working where it pulls out an averaged min and max value for
weekly, monthly time periods.

Keep in mind that I am used to working with relational databases and can
just query the database for an exact minimum value for a certain time

Maybe I am way off base on the functionality of rrdtool.

I don't know if I can set my rrdtool database up differently to achieve this
or not.

Sorry if I am confusing the issue here.


-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at slot.hollandcasino.nl]
Sent: Friday, September 07, 2001 4:43 PM
To: Kempf, Reed
Cc: rrd-users at list.ee.ethz.ch
Subject: Re: [rrd-users] functionality question

Kempf, Reed wrote:
>         rrdtool graph - \
>         --start ${RRDDATE} \
>         --title ${TITLE} \
>         --vertical-label load_time \
>         --imginfo '<IMG SRC="img/%s" WIDTH="%lu" HEIGHT="%lu"
>         --imgformat PNG \
> DEF:load_time=/home/rrdtool/data_bases/${NUMBER}.rrd:load_time:AVERAGE \

Here you ask for averages ...

> Is there a way to graph the true MIN and MAX values for weekly, monthly
> yearly time periods.  

Sure.  DEF:....:MIN  and DEF:....:MAX

It is important to understand that each CDP is an average, by nature.
When multiple CDPs have to be aggregated into a new one (for instance
due to graphing but also due to consolidating) the minimum of the CDPs
to aggregate is stored in the MIN RRA, same for average and max.

When the data is prepared to be printed (PRINT) or graphed (or GPRINT)
the same happens.

So, for a series of 3,5,7 that needs to be aggregated into one new
value (called x):

When the DEF used MIN:      x=3
When the DEF used AVERAGE:  x=5
When the DEF used MAX:      x=3

When 9 values are used to build a 3 pixel wide graph:
(I know, absurd example, it is just for the discussion)

Values are: 1 2 4 8 16 32 64 128 256


Since the graph is only 3 pixels wide, the 9 values will have to be
consolidated.  a,b,c become: {1,8,64}, {2.33,18.67,149.33}, {4,32,256}

This will print the minimum of the minima: 1.00
This will print the average of the minima: 24.33
This will print the maximum of the minima: 64.00

The minimum of the averages: 2.33
The average of the averages: 56.78
The maximum of the averages: 149.33

The minimum,average,maximum of the maxima: 4,97.33,256

Note: values above may have been miscalculated by me, I didn't use
RRDtool to produce them.

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