[rrd-users] Re: A little help with creating RRDs from scratch

[Alex van den Bogaerdt]

J. Michael Lipsey wrote:
> 
> First off, I'm not sure if this is the correct forum or if I should send
> this question to the developer's forum...let me know.

No, the developers list would not have been the right choise.
If you want to hack the code or participate in the discussions
on that subject, you're welcome there.  From RRDtools perspective,
you're a user, not a developer.

[snip]

> My problem is creating the initial database that will allow me to poll the
> way I want. I am just not sure exactly what the best way to set up the
> database is.
> 
> Here is what I have to create the database so far:
> 
> $rrdtool create  /opt/mrtg/var/$ubrs/$g\.$i.rrd --start $startime
> DS:number:GAUGE:900:0:500  RRA:MAX:0.25:1:500

This expects a number ( 0 <= x <= 500) every 15 minutes.  If you enter
a number outside the range, or after that 15 minutes, you'll be entering
a NaN automagically.  However, since you used the default step size you
will be storing your data in 5-minute time slots.  So, if you update at
exact 15-minute intervals you'll be filling 3 PDPs per update.

>          I think my main difficulty is the RRA. I would like it to show the
> MAX, that is all that matters since I'm just counting them up and putting
> that number into the database. All of the numbers input are MAXes and no
> averages are needed. Then there is 0.25 for every quarter hour, I'm not sure
> what I should put for the "Steps" or what I should have for the "Rows".

MAX has to do with the consolidation functions.  If two (or more) values
have to be consolidated into one, you'll be using the highest of them
in stead of the average.  This can be right, if this is what you want.
Over time you will probably have one pixel per day (so: one value per day)
and this will show the highest number seen during that day.

You've set xff to be 0.25 and this means 1 out of 4 values may be unknown
while still producing a valid entry in the RRA.  I don't think it matters
much on an RRA with just one PDP per CDP.

You've set the number of PDPs per CDP to 1.  Each row in the RRA will thus
be 1 PDP long (which is 5 minutes in your case).

You've set the number of rows in the RRA to 500, the total duration of the
RRA will thus be 500*5 minutes is 2500 minutes is 1d17h40m.

> I want to be able to create a weekly, monthly and a yearly graph from these
> RRAs.

Please read the tutorial for more information.  You're close, but not
quite yet there.

HTH
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