[rrd-users] YANQ - Yet Another Newbie Question - Once a day gauge

Brander, Eric Eric.Brander at ACS-INC.com
Fri Nov 22 19:22:41 MET 2002

Even after reading man pages and the most excellent tutorial, I'm at a loss.
For my first RRD I want to track a number once a day, and be able to produce
a # per day kind of graph.  Seems simple, but for some reason I can not get
it right.

Scenario:  Once a day I want to have a number entered in to an RRD.  I want
to store these numbers for 5 years.  1825 data spots at an interval of 86400
(1 day) seconds. In case I miss a poll or the polling is late, I've allowed
a window of an additional day (up to 172800 seconds) to accept data. (I
think that's how it works) So, I create a database:

rrdtool create test.rrd --step 86400 DS:Count:GAUGE:172800:U:U

I don't really want to average anything, I don't want any consolidations, I
just want it to store my numbers as I have given them.  So, I'm really
confused on the RRA: section.  Using the MAN pages and the tutorial I came
up with what I did, but honestly I do not know why.

SO, with that command I have an RRD called test.rrd.

I've input some data, added a day's worth of seconds between readings.
Count starts at 0, then 100, 200, 400, 900, 1200 for the subsequent days.

I can generate a nice little basic graph on this data! Yahoo!  I use the
following that I mangled and extracted from the tutorial:

rrdtool graph test.gif --start 1037836800 --end 1038389574
DEF:Count=test.rrd:Count:AVERAGE LINE2:Count#555555

I'm not yet sure why I need to have the word " Count" in there so many
times, nor do I know why I'm using LINE2 (what happened to LINE1?) -
regardless, I'll bang the MAN pages some more for those answers.

Here is where I really really get confused.  I want to create a graph image
that shows and displays in text the count per day.  I thought I could do
this math at GIF creation time, but I'm really losing faith in my original
thinking.  Can I do this kind of graphing an RRD that is essentially a
GAUGE?  Should I start over and create an RRD that is a COUNTER and not a
GAUGE so that it will do the daily math for me?  Will it do the math for me?
I figured if I used the gauge I could make it give me a report for a day,
month, or even year with the correct parameters - but I can't seem to figure
that part out.

Does anyone have an example of creating graphs like this and what the RRD
should look like?

By the way, in case you were wondering, I am going to be charting page
counts on some of our high-priority, high-maintenance printers. Currently I
use MRTG for the task, but I want a lot more flexibility for my charting,
and I don't want to poll every 5 minutes.  Also, I fooled myself in to
thinking this would be an easy RRD to start and learn with - haha.

Thanks in advance for your input.


P.S.  A reply along the lines of "RTFM NEWB GOWAY KTHXBYE" is really not
needed here. I think I've proven that I've at least attempted to get what I
need and have at least tried some self-help - so spare me the lecture and
just help if you can.  

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