How to graph iostats?

I have a server with some performance issues, and we'd like to graph disk access (as opposed to utilization). iostat provides the raw data. I see references in hobbitgraph.cfg to an iostat graph type. I see iostat in the TEST2RRD and the GRAPHS variable. I don't know how to feed the raw data to hobbit so that the graph will appear.

I tried loading the bb-iostats.sh script, which creates a nice green dot called vmio, but no graphs...

Can somebody lend me a clue-by-4? I'm certain I'm missing something terribly trivial, but I've spent most of my effort with hobbit on monitoring routers, and very little on hosts.

-- Daniel J McDonald, CCIE # 2495, CISSP # 78281, CNX Austin Energy http://www.austinenergy.com