Intel i915G User Manual page 82

Appendix
The RAID limitations are shown as below.
Stripe (RAID 0):
There isn't any specific limitation.
Mirror (RAID 1):
Two hard drives that form a RAID 1 array have to be attached as the same master
or slave hard disks. For example, primary channel (Pri) master drive (D0) and
secondary channel (Sec) master drive (D0) can form a mirror array; primary
channel (Pri) slave drive (D1) and secondary channel (Sec) slave drive (D1) can
form a mirror array; but primary channel master drive and primary channel slave
drive cannot form a mirror array.
Stripe + Mirror (RAID 0+1):
A RAID 0+1 array has to be formed by four hard drives. RAID 0+1 is implemented
as a mirrored array whose segments are RAID 0 arrays.
SPAN (JBOD):
There isn't any specific limitation.
Normal:
If a hard drive is not included in an array (Column "Assignment" in the View
Drive Assignment is shown "Free"), this hard drive is regarded as a normal drive.
The existence of the normal hard drive sometimes will influence the array number
user specified. If the Pri/D0, Pri/D1, Sec/D0 or Sec/D1 hard drive is a normal drive,
array 0, 1, 2 or 3 cannot have the array setting respectively. However, you do not
have to concern about this limitation. If Setup Utility finds any conflicts, Array
No will be adjusted automatically. After finishing setting the array, go back to the
Define RAID Menu then you will find the Array No is changed. This is because
the existence of the normal hard drive(s) causes the Array No to be adjusted
automatically.
When you press "Ctrl-Y" keys to save your change. The following window will
appear to choose to clear the boot sector for the newly created array or not. If your
RAID Mode is neither Mirror nor Stripe + Mirror, this array setting is finished and
then you can click the "Esc" key to go back to the Define RAID Menu .
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