Raid stands for Redundant Array of Independent Disks. This is used to prevent data loss and redundant data RAID hopes prevent data loss. RAID has different levels of RAID. RAID level 1 reads the data to a set of hard drives the drives are equal should one fail you can continue with one. RAID uses half the space on the respective drives . The only limitation is the amount of drives available in your RAID storage unit.
RAID 5 has speed and protection. This RAID reads and writes data to multiple drives and moves data across multiple drives. RAID 5 uses one third of the space and needs three hard drives.
JBOD is different from the other raid methods rather than storing the same data across multiple drives it groups the drives together acting like a single drive. When one is full it moves on the the second in the same way until all drives are filled