RAID is an acronym for Redundant Array of Independent Disks. With RAID enabled on a storage system you can connect two or more drives in the system so they act as one large volume fast drive or set them up as one system drive used to automatically and instantaneously duplicate (or mirror) your data for real-time backup.
RAID 0 mode provides disk striping across all drives in the RAID drive group. RAID 0 does not provide data redundancy but does provide the best performance of any RAID levels. RAID 0 breaks up data into smaller segments and stripes the data segments across each drive in the drive group.
Set the system to data protection mode (also known as mirrored mode or RAID 1) and the capacity is divided in half. Half of the capacity is used to store your data and half is used for a duplicate copy. If one drive goes down your data is protected because it's duplicated.
In systems with three or more drives we recommend that you set the system to RAID 5. This gives you the best of both worlds: fast performance by striping data across all drives; data protection by dedicating a quarter of each drive in a four drive system to fault tolerance leaving three quarters of the system capacity available for data storage.
RAID 10 or RAID 1+0 delivers very high I/O rates by striping RAID 1 (mirrored) segments. This RAID mode is good for business critical database management solutions that require maximum performance and high fault tolerance. A system set to RAID 10 yields half the total capacity of all the drives in the array.
JBOD is the use of one or more drives not in a RAID configuration but managed as separate logical volumes. Spanning is the combination of drives in a linear fashion to create one large logical volume. The advantage of using this mode is that you can add more drives without having to reformat the system.