RAID(Redundant Array of Independent Disks)

Definition RAID: a method of storing data on multiple hard disks and collection of disk drives that are considered by the operating system as a single logical drive, Redudant disk capacity is used to store parity information to ensure recoverability of data disk failure.

    Types of RAID: 

RAID

1. RAID-0: This technique has striping but no redundancy of data. Data on the track and spread to the entire disk, RAID-0 has a High-Speed ​​Access, Data search performed parallel and Multiple data requests do not happen in a single disk.
2. RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data, Recovery is simple and Very expensive, because the cost of the
   entire disk is doubled.
3. RAID-2: This type disk Movement all synced to each other, uses striping across disks with some disks storing error checking and correcting information, stripes used very small, Often single byte / word, Multiple parity disks using Hamming Code, Redundancy disc is still too much, very Expensive and Rarely used.
4. RAID-3: There is only a single-disk redundant for all disks, only use system-Bit Parity for recovery,  The embedded error checking information is used to detect errors, High Speed ​​Data Transfer greatly and RAID-3 is best for single-user systems with long record applications.
5. RAID-4: This type uses large stripes, which means you can read records from any single drive, Each disk is operated independently and not synchronized, Bit by bit parity calculated for each disk, Parity bits are stored on redundant disk.
6. RAID-5: Parity bits spread over the entire disk, including the redundant disk, Parity Bit Allocation arranged Round robin, Prevent bottlenecks at redundant disk and Commonly used for network servers.
7. RAID-6: A second parity scheme distributed across different drives and offers extremely high fault- and drive-failure tolerance, Suitable for high volume data.
8. RAID-7: This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of a stand-alone computer. One vendor offers this system.