[rrd-users] Can a graph be created that aggregates a set of (identically structured) rrd files?

[Alex van den Bogaerdt]

> Hi folks,
> 	I am new to RRD and still trying to wrap my mind around the power of this
> excellent tool.  I am working on an application to use RRD to store
> electricity meter data for a group of homes.  I am expecting to create an
> RRD file for each home, and it will have a number of RRA's defined for
> various time periods.

Good. I suggest you store Joules, or kilowatthours.

> In addition to displaying the individual house data graphs, I would like
> to also create graphs that show aggregated results drawn from the house
> RRD files.  For example, I might show the combined power draw in watts for
> the 8 homes that make up a quadrant of my neighborhood, or show the total
> power draw from all 30 homes.
>
> Is there a reasonably-straightforward way to do this in RRD?

DEF:meter1=/home/user/data/rrd/house1.rrd:meter:AVERAGE
DEF:meter2=/home/user/data/rrd/house2.rrd:meter:AVERAGE
DEF:meter3=/home/user/data/rrd/house3.rrd:meter:AVERAGE
[...]
CDEF:total=meter1,meter2,meter3....
[...]
LINE1:total#000:total


There are several things to improve in this (incomplete) example, but what
I show here is the answer to your question: how to combine data from
several sources.

Another example (using the same DEFs):

[...]
AREA:meter1#F00
AREA:meter2#FC0::STACK
AREA:meter3#0C0::STACK
AREA:meter4#F00::STACK
[...]