This picture shows how data flows through the Graphite system. There is one component on this graph that has not yet been publicly release, namely PypeD. PypeD is a stream aggregation application that efficiently handles a large number of high-volume client connections and provides a single aggregated stream of data to Carbon. As soon as I get some time I plan on releasing PypeD under an open source license as well.
My apologies for the crudeness, I threw this together in a hurry for a presentation a few years ago.