Kimsufi has tiny cheap Atom servers with self built or made to order racks and hardware:

(This is 2011, I think it looks fancier now)

https://lafibre.info/ovh-datacenter/data-center-ovh-roubaix-...

Edit: Seems like they stopped publishing videos for that datacenter, but this seems to be a video for the burn down datacenter in 2013: https://www.youtube.com/watch?v=Y47RM9zylFY