I'm using MRTG; yeah it's a little harder to setup, but it's also less system resource hungry, and comes with indexmaker to make a basic index.html for viewing the graphs in a browser.
Cacti also gives similar graphs (RRDTool back end), I believe it uses sql database, not flat file.
Cacti also gives similar graphs (RRDTool back end), I believe it uses sql database, not flat file.