Hoard is a library for storing time series data data on disk in an efficient way. The format lends itself very for collecting and recording data over time, for example temperatures, CPU utilization, bandwidth consumption, requests per second and other metrics. It is very similar to RRD, but comes with a few improvements. Hoard is based on an existing file format called Whisper. It was designed by Chris Davis for the Graphite project and features improvements over the RRD file format. Whisper is implemented in Python and Hoard is merely a straight-forward port of that implementation over to node.js.