Asus RS100-E4/PI2 - Manual (Page 119)

ASUS RS100-E4/PI2 6-21
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 12 of the Creating a RAID set: Using Easy
Configuration section to add the new RAID configuration.