* RAID 0 (striped disks) distributes data across several disks in a way that gives improved speed and full capacity, but all data on all disks will be lost if any one disk fails.
* RAID 1 (mirrored settings/disks) duplicates data across every disk in the array, providing full redundancy. Two (or more) disks each store exactly the same data, at the same time, and at all times. Data is not lost as long as one disk survives. Total capacity of the array is simply the capacity of one disk. At any given instant, each disk in the array is simply identical to every other disk in the array.
* RAID 5 (striped disks with parity) combines three or more disks in a way that protects data against loss of any one disk; the storage capacity of the array is reduced by one disk.
* RAID 6 (striped disks with dual parity) (less common) can recover from the loss of two disks.
* RAID 10 (or 1+0) uses both striping and mirroring. "01" or "0+1" is sometimes distinguished from "10" or "1+0": a striped set of mirrored subsets and a mirrored set of striped subsets are both valid, but distinct, configurations.
* RAID 53 Merges the features of RAID level 0 and RAID level 3.
(Raid level 3 and Raid level 4 differs in the size of each drive.) This uses byte striping with parity merged with block striping.
RAID can involve significant computation when reading and writing information. With traditional "real" RAID hardware, a separate controller does this computation. In other cases the operating system or simpler and less expensive controllers require the host computer's processor to do the computing, which reduces the computer's performance on processor-intensive tasks (see "Software RAID" and "Fake RAID" below). Simpler RAID controllers may provide only levels 0 and 1, which require less processing.
RAID - Wikipedia, the free encyclopedia