RAID 0 - Block-level striping without parity or mirroring.

   Provides improved performance and additional storage but no redundancy or fault tolerance (making it not a true RAID, according to the definition).  However, because of the similarities to RAID (especially the need for a controller to distribute data across multiple disks), simple stripe sets are normally referred to as RAID 0.  Any disk failure destroys the array, and the likelihood of failure increases with more disks in the array (at a minimum, catastrophic data loss is twice as likely compared to single drives without RAID).  A single disk failure destroys the entire array because when data is written to a RAID 0 volume, the data is broken into fragments called blocks.  The number of blocks is dictated by the stripe size, which is a configuration parameter of the array.  The blocks are written to their respective disks simultaneously on the same sector.  This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking.  More disks in the array means higher bandwidth, but greater risk of data loss.

RAID 1 - Mirroring without parity or striping.

RAID 2 - Bit-level striping with dedicated Hamming-code parity.

   All disk spindle rotation is synchronized, and data is striped such that each sequential bit is on a different disk. Hamming-code parity is calculated across corresponding bits on disks and stored on one or more parity disks. Extremely high data transfer rates are possible.

RAID 3 - Byte-level striping with dedicated parity.

RAID 4- Block-level striping with dedicated parity.

   Identical to RAID 5, but confines all parity data to a single disk, which can create a performance bottleneck. In this setup, files can be distributed between multiple disks. Each disk operates independently, which allows I/O requests to be performed in parallel, though data transfer speeds can suffer due to the type of parity. The error detection is achieved through dedicated parity and is stored in a separate, single disk unit.

RAID 5 - Block-level striping with distributed parity.

   Distributed parity requires all drives but one 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. A single drive failure in the set will result in reduced performance of the entire set until the failed drive has been replaced and rebuilt.

RAID 6 - Block-level striping with double distributed parity.

   Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high-availability systems. This becomes increasingly important as large-capacity drives lengthen the time needed to recover from the failure of a single drive. Single-parity RAID levels are as vulnerable to data loss as a RAID 0 array until the failed drive is replaced and its data rebuilt; the larger the drive, the longer the rebuild will take. Double parity gives time to rebuild the array without the data being at risk if a single additional drive fails before the rebuild is complete.

RAID 10 - Stripe of multiple mirrored sets.

   RAID 10 is a stripe (RAID 0) of multiple mirror sets (RAID 1). Lets assume  you have eight hard disks.  To create a RAID 10 array, take two of the disks and create a RAID 1 mirror set with a total capacity of one disk in the array. Repeat process three times using the other six disks. Finally, create a RAID 0 array and houses each of these mirror sets. This created a RAID10, They are very redundant however there is much higher hardware costs involved along with a lot of wasted disk space.

RAID 50 - A stripe of RAID5 with Parity housed in a RAID0.

    Now we are starting to get complicated… a RAID50 is a stripe (RAID 0) of multiple parity sets (RAID 5). Lets assume you have 16 hard disks and you would like to create a super redundant RAID50, take four disks and create a RAID5 striped array with parity, just as you would a stand alone RAID5. Repeat this process three more times utilizing the remaining twelve disks. Finish by creating a RAID0 array that houses each of the RAID 5 sets. Bingo, you now have a RAID50. Extremely costly they waste a tremendous amount of disk space, they do provided a very high level of redundancy and rarely is data ever lost from these configurations.