Gigabyte GA-8I955X Royal User Manual page 17

When user selects to create a RAID set or spare drive, he or she has to select size for the set or drive. BIOS will set a default
size for it and user can use the ↑ and ↓ keys to change the size. If the physical drive has never been used to create a set or
drive by the BIOS before, the full size of the physical drive will be set as default size. Otherwise, BIOS will set default size to
the size it saved in the reserved area of the physical drive before.
If the user wants to increase the default size, BIOS will display a warning message in the help window and for user's response
before changing the default size.
SATARAID5 User's Manual
17