I'm researching viable (i.e. modern) alternatives to RRDTool, but it seems like it's never really been surpassed. There's Whisper (part of the Graphite project) which is still a disk orientated format.

I'm trying to avoid tools such as OpenTSDB which are pitched at people with dedicated monitoring infrastructure.

I'm sure for most scales something like a disk-backed (read: correctly configured) Redis instance would be sufficient, but there's no well documented prior art in this area as far as I can see?