Bas Rijniersce bas at brijn.nu
Sat Jan 11 21:17:59 MET 2003

```Hi,

> I'm about learning basics of rrdtool, but can't see through some
> (lack of searching :( ), and google index of rrdtool mailing list (*very*
> useful)

Same here, and unfortunately this list apprently low on experienced users to

> So the problem:
> While reading the official tutorial, I found that two rra's were defined
> for the example database. I'd like to citate it:
> rrdtool create test.rrd --start 920804400 \
> 		DS:speed:COUNTER:600:U:U \
> 		RRA:AVERAGE:0.5:1:24
> 		RRA:AVERAGE:0.5:6:10
>
> And, only the first rra is used in the examples. (RRA:AVERAGE:0.5:1:24)
> Could somebody draw up an example, how to get second rra to "work", how
> to use it to draw a graph.

The RRA's are just the "stores" that describe how long data will be stored with
wich resolution. So if you graph rrdtool will automaticly find what resolution
is still available. In the example the step is 300 seconds and 24 of them are
stored with this resolution. The second RRA taking 6 samples of 300 and
averaging them, ten of these new points are stored.
If you want to graph something that is less then 300*24 seconds ago the
resolution is 300 seconds, ask for something older and you will get 6*300
seconds resolution..

But i could be completelu mistaken, since I also have problems getting what I
want (see my other mails :)

> If somebody could tell more about xff, the x files factor, I would thank
> him/her. I can read the definition, but I can't _understand_ it. A short
> example would help.

My guess, for the first RRA, if 0.5*6 = 3 samples are not known the whole
consolidated point is marked unknown. Logically you would say that 0.8 means
that if 8 points out of 10 are not available it's marked as unknown. But it
could also be 1/x.. Never changed it from the defaultn 0.5

>
>
> asd
> --
> Daniel "asd" Vasarhelyi

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