It can take 4 directly via it's 4 SATA ports but I had a cheap expansion card (reused in another build) to add more. Great little board, hard to find.
eBay
Dell PowerEdge T20 Socket LGA1150 Motherboard with power adapter to support standard ATX desktop connection – compatible with wide range of CPUs like E3-Xeons v3 versions, i3-4xxx,, i5-4xxx and i7-4xxx.
eBay
HP EliteDesk 800 G4 Mini Server – Powerful, Compact, and Custom-Modified for Expanded Storage. ⚙️ Note on Mod This unit includes aminor, non-structural modification to the 2.5” caddy to enhance drive compatibility.
eBay
Apple Mac Mini Server A1347 - i7CPU with 4 Cores, and HD Drive. This Apple Mac Mini Server computer for sale was one on my personal Mac Mini's. Drive is 1TB SATA Hard Disk Drive. One of the last great customisable Mac Mini's manufactured by Apple.
eBay
eBay
Very popular, Macmini ! GREAT VALUE MAC MINI i7 SERVER. VERY RARE FUSION DRIVE WITH A 240GB SSD AND A 500GB HDD. It has been fully checked, tested, refurbished and massively upgraded. The photos show the display on a new monitor using an old keyboard and mouse.
eBay
SERVER CORE I7-3770K@3.5GHZ 16GB VENGEANCE CORSAIR RAM 3 X 1TB HDD RAPTOR HDD CORSAIR AX760 POWER SUPLY WINDOWS 10 PRO GIGABYTE GA-Z77X-UD3H.
eBay
SERVER CORE I7-7700@3.6GHZ 32 GB DDR4 RAM 2 X 2TB HDD HDD CORSAIR POWER SUPLY WINDOWS 10.
eBay