Storing massive amount of statistics

Hello,

I'm in the process of sketching a statistics package for plugging into
my Rails applications.
Currently, I just store every page-hit as a record in the database, but
this grows very fast at the unnecessary cost of performance and it is
too detailed for my needs.

From experiments with RRDTool (RRD is a system to store and display

time-series data), I've found that Round Robin Archives are a way to
store massive amounts of information about pretty much anything within
a predefined amount of space.

Does anyone have experience, hints/tips or links to information about
how to implement something like RRD in Ruby?

Thanks in advance

Gijs Nijholt