AnandTech | Samsung SSD 850 Pro (128GB, 256GB & 1TB) Review: Enter the 3D Era
The problem is that the X79 chipset only supports 2 SATA 6G ports. All additional SATA 6G ports use a different controller, not part of the chipset. For the SATA 6G ports internally, 3 and 4, a Marvell controller is used. For the eSATA 6G ports, 5 and 6, again another controller is used. These ports can not be used for raid configurations where multiple controllers are used. Only configurations where all the ports are on the same controller.