[rrd-users] Re: Changing Average value in SRG.conf to MAX

Simon Hobson linux at thehobsons.co.uk
Thu Dec 7 19:09:01 MET 2006

First off, please do NOT start a new thread by replying to an 
unrelated message - it makes the threading in mail archives rather 
odd !

Edgar Humberto Parra wrote:
>Hi guys, I was wondering the following:
>I have almost a year worth of data in my RRD files, and my manager asked
>me, if I can change the value of the graphic value of RRA from AVERAGE
>to MAX, what are the consequences of doing this?

You mean, you have existing data that has been consolidated using 
AVERAGE and you want to simply change it to MAXIMUM ?

Think about it. Suppose you fed in samples of 1, 2, 3, 4, 5 and 
consolidate them to one value, the average is 3, the max is 5. Given 
a knowledge only that the average was 3, there is NO WAY to get the 
maximum - it could be 3 (all samples the same value of 3), it could 
be 15 (samples of 15, 0, 0, 0, 0), it could be something else.

The only meaningful thing I can suggest is this (no I don't know the 
details, it's something I've never done) :

export the data from the rrd
create a new rrd with additional consolidation function (ie keep a 
max as well as an average)
import the data you exported, but only populate the average values - 
leave all the max's as unknown
adapt your graphs to show a max line as well as average(s)

Where there is no historic data, the max line will be absent (by 
default unknown values are not plotted), but as you collect new data, 
it will start to appear.

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