I've just upgraded my home Network Storage box. Until now, it was very discreet, about the size of a car radio. It lived on one of my bookcases and I was very happy with it but it could only take 2.5" sized hard drives and I've outgrown what you can fit on them.
I've ended up moving to 2x4T 3.5" drives, a Coolermaster Elite 110 case and re-using the mainboard/CPU and RAM. This is hopefully enough capacity that I don't need to look at another upgrade for a few years, and the case could take more drives if I need it to.
The Elite 110 is - by Mini-ITX case terms - pretty small, but still 6 times larger in volume than the old case. In the consumer NAS market, there are plenty of appliances that takes two 3.5" drives and are much smaller than that (such as the WD MyBook Duo, or Synology DS214). Unfortunately I could not find any cases that were of this size for a DIY build. Did I miss anything obvious?
(As to why I choose DIY, that could be the subject for a future post.)
The full boring details of the build are on the NAS system page.