Adding 2 Data Sources?

[badoignle]

Hello, I was wondering how do you go about adding 2 data sources? I've tried creating a CDEF, but I'm not entirely sure how they work. On the graph, we're graphing IOPS and have 4 (kstat read and write and disk read and write operations) sources. I'm trying to add together kstats read and kstats write into a kstats total and leave the other 2.

[gandalf]

This question is NOT really clear to me.
Where do you want to add what?
What is already in place and what do you want to achieve.

Usually, many use cases are covered by the examples discussed at the documentation linked at 1st link of my sig
R.