[rrd-users] convert AVERAGE to MAX

Simon Hobson linux at thehobsons.co.uk
Sat Dec 8 11:18:21 CET 2007

Jerome Jerome wrote:
>I changed AVERAGE to MAX, but i had to create new rrd files. Can i 
>change that and keep the old datas ? is there a rrd editor ?

>  > Subject: Re: [rrd-users] (test tool)Real-Time Monitoring with PHP 
>and RRDTool

Is this question related to the subject of the email you replied to ? 
Please do not hijack threads - start a new one. When you hijack a 
thread by just changing the subject line, we end up with threads in 
the various archives that contain unrelated subjects.

If you want to edit an rrd definition and keep the old data, you have 
to dump the file (rrdtool dump), edit the resulting XML file, then 
import the data into a new rrd (rrdtoo restore).

But note that you CANNOT magically call up information that you did 
not store. If you stored average then you CANNOT derive max from it - 
for example, if the average is 1, what was the max ? 1, 5, 10, 
something else altogether ?

You might be better expanding the rrd by adding an extra CF instead 
of changing an existing one - in which case you would have a CF with 
no values (ie all unknown) for the historical data but start 
collecting new data. When you plot this, you will end up with graphs 
that have a line starting part way across.

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