InfluxDB

Influx is an open-source time-series database that can store very large volumes of data quite quickly.

Unfortunately its interpolated queries are still a little bit slow when it comes to getting data before and after the window you are requesting, so for the moment it is still not a suggested ARDI historian product.

However we are watching the development of the project with a great deal of interest - when an efficient method of fetching interpolated data arrives, we will most likely suggest Influx for all small applications.