4 X 3.5'' HDD Tray 4-bay Disk Stack

For my OpenMediaVault OMV / trueNAS project, I need a disk stack / tray for four 3.5'' HDDs.

The plan:
Under PROXMOX, SATA drives are passed through via passthrough to a NAS VM (OpenMediaVault) and can sufficiently power a ZFS filesystem through the VM with good performance. (USB disk stacks are definitely unsuitable for ZFS!!)

My solution includes a 12cm fan at the front. Therefore, air guiding is necessary. (Closed side walls - the fins are only for aesthetics) The air can only flow backward between the drives. The top drive is only cooled from below but can radiate freely upwards...

Some M3 screws are needed to fix the front plate to the side parts and the HDDs. For mounting the fan, I have provided 5mm holes.

Project outline:
Proxmox-based Linux server with (an) free PCI slot (OCuLink or Tower).
From the bay, an HBA card with "LSI 9223 9200 9240-8i HBA FW:P20 9211-8i IT Mode ZFS FreeNAS unRAID 2* SFF SATA"
e.g. https://www.ebay.de/itm/165969457620
(the IT-Mode is important)

Addendum: The HBA OCuLink - solution also proves its worth in operation with passthrough to an (OMV) VM and is stable and very performant even under load!

A 12V power supply is needed for the drives. (Discarded (PC) power supply) and SATA multiple plugs:
SATA power cable 1 male to 5 female, SATA Power Splitter for SSD, HDD and optical drives, 15 Pin Adapter male to female supplies up to 5 hard drives, processors, 18 AWG, Black
(https://www.amazon.de/dp/B0F13M1376)

The HDDs need not only 12V but also 5V on the power supply cable, otherwise they will not start up. Therefore, I tapped the 12V and installed a voltage converter to provide the 5V:
(https://www.amazon.de/Converter-Netzteil-Abwärtsmodul-Beleuchtung-Luftaufnahmen/dp/B0DHRQT83P)

Power supply, or PC power supply:
https://www.amazon.de/dp/B0D83L6YKC
works perfectly (for little money)...
 

The M5 screws for the fan are also self-printed. (Best laid flat, for stability...)
I have now equipped the cooler frame with M5 thread... (Why not directly?????)

Case for the cards and electronics

… it turns out that the aluminum cooler on the HBA card makes sense, so the case absolutely must receive another (4cm) fan…  
(https://www.amazon.de/dp/B01CZFUOD0 <= This fan is very loud!)

The PCI Riser Card with the HBA card (without slot bracket) fits into the case.
The step-down converter can be screwed to the wall. The 4cm fan is mounted in the lid...  

The feet can be glued or screwed under the case so that the air can escape better!  

A piece of 1.75mm filament is provided as a hinge for the lid.  
(If the ends are carefully melted with a lighter flame, such a lid will work forever!)

Caution, both the HBA card and the StepDown get warm! Without a fan, I would not leave this unsupervised in the basement.
therefore:

This is a DIY project, rebuild at your own risk!
 

Tools:

(previous projects)
:-)
 

Third Hand:
https://www.thingiverse.com/thing:7012826

and even older -
Vise:
https://www.thingiverse.com/thing:5961878

Solder Dispenser:
https://www.thingiverse.com/thing:5438685