Asus RS120-E4/PA4 - Manual (Page 114)

6-8 Chapter 6: RAID Configuration
6. Select RAID from the Logical Drive menu, then press <Enter>.
7. Select the RAID level from the menu, then press <Enter>.
You need at least two identical hard disk drives when creating a RAID 1 set.
8. When creating a RAID 1 set, select Stripe Size from the Logical Drive menu,
then press <Enter>.
When creating a RAID 0 set, proceed to step 10.
9. Key in the stripe size, then press <Enter>.
For server systems, we recommend that you use a lower array block size. For
multimedia computer systems used mainly for audio and video editing, we
recommend a higher array block size for optimum performance.