At a previous job we were using Ganglia (http://ganglia.sourceforge.net/ http://ganglia.sourceforge.net/) to collect both system metrics and custom metrics from

At a previous job we were using Ganglia (http://ganglia.sourceforge.net/ http://ganglia.sourceforge.net/) to collect both system metrics and custom metrics from our servers. At my current job, we still use Ganglia for redundant storage of our metrics, but then we feed the data into Graphite (http://graphite.wikidot.com/ http://graphite.wikidot.com/) for graphing. Graphite uses Whisper for it's storage mechanism. It's very similar to RRD. The author wrote a page about why he decided to write his own instead of leveraging RRD (http://graphite.wikidot.com/whisper http://graphite.wikidot.com/whisper). We've got over 60k metrics in our system; happy to talk shop if you want more info.