Basically all UPS use 12 V batteries, then they convert that to 230 V AC and server power supply converts it back to 12 V DC (main rail). Seems a bit dumb? So I decided to power all servers directly from 12 V and see how it goes.

You can find plenty of these 12V PSUs on ebay so I decided to give that a try. And to my surprise they work exceptionally well. The small power supply you can see in the picture above can supply up to 300 W of power.

12 V was provided by generic PSU which was mounted on a board with arduino and relay for switching on batteries in case of mains power loss.

With 4 servers running (light load) it was drawing somewhere about 130 W. Not bad I should say. I don’t think it would be possible if each server had regular 230 V power supply on it. By having single large power supply you can easily win on efficiency.

Server room has been running for over 3 years now without any downtime.

Some facts about server room:

  • Firewall server running pfSense
  • FreeNAS server with RaidZ2 (6x 1TB disks)
  • i7-4770 32GB server running VirtualBox with web interface.


I have experimented with oVirt and OpenStack virtualization frameworks but decided that they are too bloated for home server use and decided to simply go with VirtualBox and its web interface (which I really like). Give it a try.

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