[rrd-developers] Yet another RRD merge script

Richard A Steenbergen ras at e-gerbil.net
Fri Aug 31 18:55:32 CEST 2012

On Mon, Aug 20, 2012 at 12:53:08AM +0000, Steve Shipway wrote:
> Unable to find a script to merge my RRD files as I wanted, I've taken 
> to writing my own generic one.
> This new script will merge one or more RRD files, which do not need to 
> have the same DS or RRA definitions, to make a single RRD.  It can 
> preserve a configurable list of DS over the set, building different 
> RRA from whichever available RRA match the closest, merging RRA where 
> they cover different time windows.  You can specify longer or shorter 
> RRA length, and even change the step value as you go (though this is 
> not yet working quite right).  It should also be able to use one RRD 
> to fill in the gaps in another, though this is still work in progress.

One feature I would love to see implemented in a merge script is the 
ability to sum the data samples from multiple .RRD's. The current 
scripts are all more "splicing", i.e. picking the data from one .rrd 
file or the other, but I haven't seen anything capable of actually 
merging counters from multiple sources into a single aggregate.

Normally we do aggregation of multiple interfaces at display time, with 
a VDEF, but this doesn't cover every case. For example, imagine you're 
combining several individual interfaces into a LAG going forward, but 
still want to preserve all the historical data from the member 
interfaces. The only way to handle this without the ability to truly 
merge the data is to keep the old .RRD's from the previous interfaces 
files around forever, which is a real mess to manage.

Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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