RAID Levels

RAID 1 (Mirrored) - For entry level data redundancy. RAID 1 uses a set of disks (2 disks minimum) without parity and provides fault tolerance from disk errors and single disk failure. The array will continue to operate as long as at least one drive is functioning.

RAID 5 (Striped) - The Striped Set uses at least 3 disks (minimum) with distributed parity. Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.

RAID 10 (Mirrored/Striped) - Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In RAID-1+0, the data is mirrored and the mirrors are striped. RAID 10 is often the primary choice for high-load databases, because the lack of parity to calculate gives it faster write speeds.