Asus Motherboard P5MT-S - Manual (Page 117)

ASUS P5MT-S 5-17
6. Follow steps 6 to 7 of the Creating a RAID set: Using Easy
Configuration section.
7. Select Size from the Logical Drive menu, then press <Enter>.
8. Key-in the desired logical drive size, then press <Enter>.
9. Follow steps 8 to 13 of the Creating a RAID set: Using Easy
Configuration section to add the new RAID configuration.