Wouldn't the drive performance be significantly inhibited by RPi's USB 2.0 interface? A small board with SATA or USB 3.0 would be much faster.
https://www.aliexpress.com/store/product/NEW-orange-pi-plus-...
I hope there is more in the future to come in this area to bring the notion of home owned appliances instead of the cloud. Specially with IoT around the corner - those devices should communicate to a home server like this only.
NAS boxes are relatively popular, and the major vendors are heavily leaning on making them the "all-in-one" home/soho servers as demonstrated by the wide range of applications available to them:
We've made the box hardware-compatible with the oDroid C2 so people have an upgrade path - I understand Linux 4.10 will have out of the box oDroid C2 support so it shouldn't be too much after that that Canonical's Ubuntu Core will support it, too, and users can pick one up if they like.