it says on that mediasonic link

Important Note: • For eSata connection: Make sure your eSata port Support port multiplier. Most onboard eSata and some eSata PCI-E card only Support up to 5 drives. To see all 8 hard drives in eSata you need a eSata PCIe card that supports 8 drives.

I’m assuming the enclosure doesn’t do any of the raid/array configuration, it just passes data through.

as far as I know only USB and eSata can do port multiplying. Sata can’t. I think if you want to get access to all the drives you’ll have to get a pcie card to handle the eSata or just use USB3. eSata (6gb/s) is faster than USB3 (5gb/s) and you might actually manage to saturate the connection trying to read or write to 8 drives though one cable.