Asus DSBF-DM/SAS - Manual (Page 126)

5-16 Chapter 5: RAID configuration
4. Select all the drives required for the RAID set, then press <Enter>. The
configurable array appears on screen.
5. Press <F10>, select the configurable array, then press <SpaceBar>.
6. Press <F10> again, and select RAID from the Logical Drive menu, then
press <Enter>.
7. Select the RAID level from the menu, then press <Enter>.