So this has been driving me mad since I installed Mac OS X 10.7… Any time Cacti tried to output a graph, it would output, but it was painfully slow (like 30 seconds)… prior to installing 10.7, it was a fraction of a second.
Anyway… long story short is apparently RRDtool pulls the list of fonts from the system, and since it was running as the _www user, it was unable to write a the font cache to disk to make future font access fast.
Logging in as root and running the “fc-list” command to get a list of installed fonts fixed the problem. The first time it ran it took 30 seconds (imagine that! heh), and subsequent times it was instant. And Cacti graphs are back to being instant. Hopefully this helps someone…