Our professional 2u storage server will take motherboards from ITX up to Extended ATX. It has 3 fans that connect to a backplane fan header with a single cable , this allows BIOS control of the fans which will remain at a low noise level unless your system gets hot.
It has a 6Gb backplane which supports SATA/SAS/SSD drives both 2.5" and 3.5". If your using a raid card that supports SGPIO the caddy signal lights can help locate a problem drive. The backplane has three mini SAS ports to control the twelve drives, As twelve port raid or H.B.A cards are not common in low profile format a common setup is an eight port and the other 4 caddies connected to the motherboard using a reverse breakout cable.