[rrd-users] Change RRD Graph Definitions

Simon Hobson linux at thehobsons.co.uk
Tue Apr 3 13:29:59 CEST 2012

James McDonald wrote:

>I think I found what I needed from this thread too: 
>http://community.zenoss.org/docs/DOC-4426.  Newly created graphs now 
>seem to produce the LAST value as I want.
>Is it possible to update the existing (old) graphs to include the 
>LAST value from now on, or do I need to start with fresh graphs and 
>lose the history (even though it is AVERAGE)?

I assume you've added a LAST consolidation to your RRDs ?
Naturally this will be empty for all time prior to when you started 
adding data to it.
What I have done in the past when I've had a change is to plot two 
different series. IIRC I'd needed to change my RRDs, and created new 
ones while keeping the old ones. I think I did something like this :

AREA:a2 ...
AREA:b2 ...

Where ${switch} is a shell variable (this was in a BASH CGI script) 
representing the fixed time when the change occurred. The result is 
that it plots "a" up to the switch, and "b" from then, with a 
vertical line to note the demarcation.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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