If you know MRTG, you can think of RRDtool as a reimplementation of MRTGs graphing and logging features. Magnitudes faster and more flexible than you ever thought possible
RRD is the Acronym for Round Robin Database. RRD is a system to store and display time-series data (i.e. network bandwidth, machine-room temperature, server load average). It stores the data in a very compact way that will not expand over time, and it presents useful graphs by processing the data to enforce a certain data density. It can be used either via simple wrapper scripts (from shell or Perl) or via frontends that poll network devices and put a friendly user interface on it.
RRDtool is available for download from this site. Currently it compiles on a number of different Unix platforms as well as on NT. No binaries are officially provided at this point in time.
RRDtool is not a replacement for MRTG, as it does not implement the frontend and data aquisition features of MRTG (MRTG can be configured to use RRDtool as its database backend and together with a cgi grapher like 14all or mrtg-rrd all your mrtg graphs can be generated on demand). If you can program yourself you can use RRDtool right out of the box or if you don’t program you can use one of several frontends which use RRDtool.