I would believe you are referring to our Intel® Server Board S5520UR. Would you happen to know which server system you are using? The reason I ask is that depending on the server system you may have an Active Midplane board acting as your RAID controller instead (Storage Options).
If the RAID controller is the onboard Intel® Server RAID Technology II (ESRT2), make sure that the drives are configured properly. Let me remind you that even if you use individual drives you would need to configure these as individual RAID 0 drives.
If needed, you may use the following RAID Simulator Tool to assist you on configuring your RAID array.