[rrd-users] trying to understand the relationship between source data, what's in rrd and what gets plotted

Alex van den Bogaerdt alex at ergens.op.het.net
Sat Jul 21 19:10:56 CEST 2007

On Sat, Jul 21, 2007 at 09:42:47AM -0400, Mark Seger wrote:

> Just put the dots (or lines) where they belong and if some fall on top 
> of each other and you only see 6, that's just fine.  Where I'm coming 
> from, and what I always do with performance related data, is look at a 
> broad range of time, perhaps a day wide.  I want to look at everything 
> from cpu load, network, disk, memory usage, infiniband loading and a 
> whole lot more.  I want to be able to see at a glance if there are any 
> spikes where there shouldn't be or drops that also shouldn't be there.  

So: a line from minimum to maximum, together with a normal, would be
good enough for this purpose.

> If nothing shows up, I'm done and that's why it's so critical that 
> everything be displayed.  If there is a problem THEN I want to zoom in 
> and the resolution becomes more significant and those dots/lines then 
> begin to spread out as the resolution increases.

Assuming a 400 pixel wide graph:

At first you are looking at 400 days.  One of them is showing a high
average.  Then do as you say right now: zoom in on the data. If you
make sure you have the data available in your RRA, RRDtool is able to
display it. E.g. the next graph you display shows 4000 seconds (10
per pixel column). Select the problem area and display 400 seconds
(1 per pixel column).

(N.B. _how_ to select the appropriate area, and how to zoom in, is
a function of a front-end application, not RRDtool).

Either I don't get what you're after, or you don't get that rrdtool
will do as you say (right now).

> begin to spread out as the resolution increases.  Quite frankly I don't 
> look at consolidated data because it's those exceptions that are the 
> most significant when trouble shooting.

Those exceptions will be higher than normal or lower than normal.
These are propagated if you select "MIN" or "MAX" instead of "AVERAGE".

You want it and RRDtool is able to deliver it if you ask it to.

Alex van den Bogaerdt

More information about the rrd-users mailing list