It is running for almost 3 years now, maybe one likes what i did and might take it as inspiration for an upcomming NAS project.
Board: ASRock AM1H-ITX, Bios 1.50 (DC/DC Power)
CPU: AMD Athlon 5350 passive running @ 1,13 Volts @ 48°C max. @ full load, summer 33°C room temperature,
RAM: 2x 8GB Crucial Ballistics Sport VLP 1.35 Volts
Power: FSP NB Q90 P 90 Watts 19 Volts
OS-Drive: 32 GB mini SLC USB thumb drive
Storage: 3x6 TB WD Red Raid 5, vibration-cushioned mounting
(storage is powered directly by mainboard. original cable supports only 2 drives, i made my own with 3 ports on it.)
Case: IKEA Alex, white, drawer air sealed as far as possible with window sealings, silicone and acrylic plates on top
Cooling: Arctic Alpine M1 passive, 2x Noctua NF-B9 redux (350-1600 rpm, PWM)
OS: OMV 3.0.83
Idle ~19 Watts, all disc running, I don't park them, but use low performance/low noise setting within AAM.
Services: SMB, Teamspeak, Calibre ebook server, DLNA, Nextcloud, Luks, USB-backup on hotplug
I cut a foam rubber sheet to fit mainboard + cooler profile, so that all air from left chamber has to travel through cpu cooler. Another foam rubber profile lies under the mainboard as well. Dust protection is installed twice: one within the front grid and a second fine filter within the left pre chamber. Both are easy to clean. Air stream enters on left side, cools the discs, passes cpu and tangent power supply and leaves on right side. I set up temperature profiles for both fans, left fan has for all temperatures a 10% higher speed so that a little excess pressure is within the two chambers.
Sorry, I did not take pictures during build process, it took probably a week, a couple hours each day after work to set everything up.