RRDtool is the OpenSource industry standard, high performance data logging and graphing system for time series data. It was created by Tobias Oetiker and is still very actively supported. Find documentation and tutorials to learn about features and parameters. RRDTool is one of the building blocks of Cacti. It stores all performance data for graphing with Cacti.
This chapter shows some information about specific rrdtool features that are not covered in other chapters. Even when not using Cacti (yet), you may find it helpful for a better understanding.
The rrd files are designed to never grow in space, even if you constantly feed data to them. How come? There's a buitin compression feature; rrdtool calls this consolidation. Read on to understand this better.
By default, a rrd file holds more than one consolidation level. The initial layout, defined when creating the file using rrdtool create, is such (courtesy engeishi):