Anybody doing DIY NAS? Or transformed old PC into NAS?

I have an Atom miniPC at home and planning to transform it into NAS.

I'm also looking for automated FTP process scripts to download files from servers into the NAS.

As for the OS/Software, I've tested Ubuntu-Server and currently stuck at installing FreeNAS with BTX halted error. Decided to try FreeNAS as it is very popular among NAS DIY'ers.

Taking it as practice to understand more.