Asus RS100-E4/PI2 - Manual (Page 124)

6-26 Chapter 6: RAID Configuration
5. When prompted, press the <SpaceBar> to select Yes from the
Initialize? dialog box, then press <Enter>. You may also press <F10>
to initialize the drive without confirmation.
6. A progress bar appears on screen. If desired, press <Esc> to abort
initialization.
7. When initialization is completed, press <Esc>.