RRDtool refers to round robin database tool.  Round robin databases have
a fixed number of data points in them and contain a pointer to the
current element.  Since the databases have a fixed number of data points
the database size doesn't change after creation.  RRDtool allows you to
define a set of archives which consolidate the primary data points in
higher granularity.  RRDtool is specialized for time series data and can
be used to create RRD files, update RRDs, retreive data from RRDs, and
generate graphs from the databases.  This module provides a POE wrapper
around the rrdtool command line interface.
