Redundant Array of Independent/Inexpensive Disks (RAID) is a method of combining multiple hard disk drives so that they appear as one hard disk to the operating system. This combination of disks is called an array.
RAID has two main benefits available, depending on the type of RAID chosen. These are performance and redundancy.
RAID Level 0 (striping) provides greater performance than that of a single disk. However, it has no data redundancy. The RAID controller writes data fragments across all disks in the array. The ability to read and write from multiple disks at the same time results in a performance increase. However, since the data is broken into fragments spread across all disks, there is increased data risk. If one disk in the array fails, all data is inaccessible and may be lost.
Raid Level 1 (mirroring) provides full redundancy, but gives no performance benefit over a single disk. Each RAID 1 array is two disks, one being a copy (mirror) of the other. If one disk fails, the other will contain the same data. Though RAID 1 provides better data protection than a single disk drive, important data should still be regularly backed up.