As another point of reference, I have a ProLiant Microserver running FreeBSD with 4x3TB drives in RAID-Z. I installed a custom BIOS that removes the limitations on the optical SATA port and run a small single drive for the OS off that.

It's a dream to use and gives me 8TB of usable storage. I can easily hit saturation of the NIC and it's nice and small and quiet, fitting in the bottom corner of my bookshelf.