# [rrd-users] Re: I need help to create a specific rrd file (LONG EMAIL)

Iñaki Martínez sistema at euskal-linux.org
Mon Jun 2 12:13:19 MEST 2003

```Hi Alex van den Bogaerdt!!!

hey me again Alex.... :-)

Well this time instead of a rapid answer with more stupid questions i have,
during this weekend, re-read your tutorial three times, again........

And i think i understand better how rrdtools works.......

I have made two formulas, one for graph width and other for calculating
rows.

Step by step.......

--------------------------------------------------------------------------------

* Graph width:

width = (time to show in seconds) / (seconds per pixe)

Example: to show 25 hours with 4 minutes per pixel

(25 * 60 * 60) / (4 * 60) = 375 pixels width

--------------------------------------------------------------------------------

* calculating rows:

minutes 1 day
rows = (time in days) * --------------------------
steps * (step in minutes)

Example: 5 years, step each minute (=60 segs), 1 steps

1 * 24 * 60
row = (365 * 5 + 2) * -------------- = 2630880
1 * (1 * 60)

RRA:AVERAGE:0.5:1:2630880
RRA:MAX:0.5:1:2630880

--------------------------------------------------------------------------------

> Either use the first created RRA to generate the graph, or create an
> RRA which covers the desired time span (5 years) in the resolution you
> are going to graph it.

> It is enough to only have the 1st RRA (one time for AVG, one time for MAX)
> and use it to create all graphs.  Using extra diskspace by generating the
> other RRAs will result in less time spent while generating the graphs.

I have one question (i hope not be stupid):

If i create one RRA for each graph i want, making each RRA to "accommodate"
each graph and some time after i want to change the aspect of the graph,
then that RRA is worthless????

Example:

RRA:AVERAGE:0.5:25:105236

rrdtool graph file.rrd --start now-8d --height 150 --width 461

25 minutes per pixel

Then instead of 25 minutes per pixel i want 30 minutes per pixel:

rrdtool graph file.rrd --start now-1w --height 150 --width 384

In this case the above RRA is useful or useless, in case of useless i think
then it is better only the first RRA (RRA:AVERAGE:0.5:1:2630880)

Am i correct??????

> BTW this results in a huge database.

OK, there is unused space.... :-)

> You should answer the question:  Do I want to trade diskspace for speed?

OK, i want to trade diskspace for speed.......

--------------------------------------------------------------------------------

If all of the above is correct i will creat the following RRD file:

rrdtool create network.rdd --step 60
DS:in:DERIVE:600:0:4294967295
DS:out:DERIVE:600:0:4294967295
RRA:AVERAGE:0.5:1:2630880
RRA:AVERAGE:0.5:3.5:751680
RRA:AVERAGE:0.5:25:105236
RRA:AVERAGE:0.5:36:73080
RRA:AVERAGE:0.5:456:5769
RRA:MAX:0.5:1:2630880
RRA:MAX:0.5:3.5:751680
RRA:MAX:0.5:25:105236
RRA:MAX:0.5:36:73080
RRA:MAX:0.5:456:5769

and the following graphs:

* Hourly (show 3,5 hours)

rrdtool graph file.png --start now-3h-30m --height 150 --width 420

* Dayly (show 25 hours = 1 day + 1 hour)

rrdtool graph file.png --start now-25h --height 150 --width 429

* Weekly (show 8 days = 1 week + 1 day)

rrdtool graph file.png --start now-8d --height 150 --width 461

* Monthly (show 31 days = more or less 1 month)

rrdtool graph file.png --start now-31d --height 150 --width 496

* Yearly (show 366 days = more or less 1 year)

rrdtool graph file.png --start now-366d --height 150 --width 462

* 2 years (show 366 * 2 days = more or less 2 years) big graph

rrdtool graph file.png --start now-732d --height 150 --width 924

* 1 day in hours (show 25 hours) very big graph!!!!

rrdtool graph file.png --start now-24h --height 150 --width 3000

NOTE: this last graph is better shown with scroll layer :-)

Thanks all and specially to Alex!!!!

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