I've purposely build that NAS around two or three years ago. It's a Gigabyte B360M D3H mainboard, Intel Pentium Gold G5400 and 16GB of the cheapest RAM I could find. An Adaptec 71605 card provides SAS/SATA connections for up to 16 drives and a Mellanox Connect-X3 connects my NAS via 10Gbit/s to my network. The case is an Inter-Tech IPC 4U-4424 . It has 24 hot swap bays. But I would not recommend it because the backplane is terrible. Four or five slots are not working. Sometimes, when I re-insert a drive, it is not detected.

Using cheap RAM bit me in the ass last year as one of the RAM sticks started to fail. I didn't notice that there is a problem with the RAM at first. Only when I observed that one of my scripts was not working I started to investigate the problem. Turns out that one of the RAM sticks failed. Re-inserting the stick did not resolve the problem so I replaced all sticks with old Crucial RAM I had laying around. Some files that I transfered to the NAS during that time period are corrupt. In the future I won't use cheap RAM anymore and I'm also currently planning to replace the mainboard and CPU with something that supportes ECC RAM so that I can be notified when on of the sticks starts to fail.

Here are some pics from building the NAS