ASROCK 775DUAL-880PRO Manual To Installation And Configuration page 5

RAID 1 (Data Mirroring)
RAID 1 is called data mirroring that copies and maintains an
identical image of data from one drive to a second drive. It
provides data protection and increases fault tolerance to the
entire system since the disk array management software will
direct all applications to the surviving drive as it contains a
complete copy of the data in the other drive if one drive fails.
JBOD (Spanning)
A spanning disk array is equal to the sum of all drives. Spanning
stores data onto a drive until it is full then proceeds to store files
onto the next drive in the array. When any member disk fails, it
will affect the entire array. JBOD is not really a RAID, and it does
not support fault tolerance.