I bought a mini-ITX board with 4 SATA ports and an embedded CPU. I added a PCIe card with 2 additional SATA ports. I bought a mini-ITX case with mounts for 6 HDDs. I have 5 8TB drives (RAIDZ2) and 1 SSD as the boot drive. The system runs Ubuntu Server.
I found this setup a lot cheaper than the dedicated NAS boxes you can buy and more flexible.
I found this setup a lot cheaper than the dedicated NAS boxes you can buy and more flexible.