Asus RS120-E4/PA4 - Manual (Page 135)

ASUS RS120-E4/PA4 6-29
6.2.8. Selecting.the.boot.drive.from.a.RAID.set
You must have created a new RAID configuration before you can select the boot
drive from a RAID set. Refer to the Creating a RAID set: Using New Configuration
section for details.
To select the boot drive from a RAID set:
1. From the Management Menu, select Configure > Select Boot Drive, then
press <Enter>.
2. When prompted, press the <SpaceBar> to select the bootable logical drive
from the list, then press <Enter>.
3. The logical drive is selected as boot drive. Press any key to continue.