Move PCI-E HDDs to Mobo Sata3 for Performance?

Hey,

I have a PCI-e x4 to 8 SATA connector to connect 8 HDD over the PCI-E 3.0 x4 interface. I have 3x Sata3 ports open on my mobo and I’m wondering if I should take 3 of the drives and move them over to the mobo for performance. If I understand correctly the sata3 interfaces have a 6Gbps connector on individual backbones, and the pci card has 4Gbps shared between the 8 drives, 4 lanes of 1Gbps each. Wouldn’t it make sense to move 3 of the drives to the mobo for a small performance gain?