Hi, this is a repost from elsewhere [1] - TL;DR at home for years now I have been using an older QNAP TS-459+ with 2 GB and 4 drives RAID5 that worked with the vendor-supplied QNAP shrink-linux and busybox, and I've had it with that. I wanted up to date packages, a full linux so backed up everything and replaced QTS with a nice and smooth OMV. That is why I am here now. 
That QNAP device is x86_64, has a miniITX board, dual GB-LAN, USB and eSATA and overall okay hardware specs for a home server. So getting started was easy as pie, including fancontrol and such. OMV appears to be very well done!
Some requirements and services I had set up before transitioning to OMV:
- AFP, NFS, SMB/CIFS file server
- per-user permissions for those files
- TimeMachine backup
- DLNA server to use contents on streaming clients in the home network (a smart TV, and other devices)
- storage used is around 3TB of data (music, photos, handful of ISO files)
- a teensy web server serving static pages only
Moreover I had
- ipkg-installed goodies like dovecot, postfix, an additional and customized SSHd, version control software, Apache
- a Minecraft server running with < 10 users
- used to have a remote sync setup via ssh and rsync, but no MTRR
- wanted to use Owncloud or similar I'd want to have MariaDB setup, but vendor policy denied us access to the system MariaDB
So, while expecting little difficulty in the process I would invite discussion about similar projects and experiences with other similarly small-scane QNAP-built devices here.
I try to put OMV on everything I can install Debian on. OMV runs great on the TS-451.