SATA-II spec allows for hubs that can connect 4 drives to an existing port, however they'll share bandwidth.
If you're doing serious RAID you might want to look up 3Ware, RaidCore, and Areca instead of playing with the onboard toy RAID that barely works.
If you're doing serious RAID you might want to look up 3Ware, RaidCore, and Areca instead of playing with the onboard toy RAID that barely works.