Asus RS160-E4/PA4 - Manual (Page 122)

6- 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 DWC from the Logical.Drive menu, then
press <Enter>.
When creating a RAID 0 set, proceed to step 10.
9. Select On to enable the Disk.Write.Cache setting, then press <Enter>.
Enabling DWC can improve the performance, but with the risk of data loss.