What is "rrdtool"

RRDtool (acronym for round-robin database tool) aims to handle time series data like network bandwidth, temperatures, CPU load, etc. The data is stored in a circular buffer based database, thus the system storage footprint remains constant over time. Note that this is distinct from the computer science concept of round-robin scheduling.

It also includes tools to extract RRD data in a graphical format, for which it was originally intended.

Bindings exist for Perl, Python, Ruby, Tcl, PHP and Lua. And there is an independent full Java implementation, rrd4j.