Introduction to Redundant Array of inexpensive (or Independent) Disks (RAID)
Redundant Array of Inexpensive (or Independent) Disks (RAID) basically involves combining two or more drives together to improve the performance and the fault tolerance. Combining two or more drives together also offers improved reliability and larger data volume sizes.
The main Redundant Array of Inexpensive (or Independent) RAID types are listed below.
RAID 0 makes it faster to read and write to the hard drives. But data redundancy is not available in RAID 0. If one of the disks of which the striped volume consists fails, then the entire volume fails. RAID 0 requires minimum two hard disks.
Since reads and writes to the hard disks are done simultaneously, the performance in increased. RAID 0 is also known as striping without parity.
RAID1 mirrors information between two disks. If one disk is failed, the data can be recovered from an exact replica which was mirrored on another disk. The disadvantage of RAID 1 is reduced performance, since data has to be written twice. RAID 1 is expensive also since an additional hard disk for every hard disk worth of data. RAID 1 is also known as disk mirroring.
RAID 5 is also known as disk striping with parity. Minimum three disks are required to implement RAID 5. RAID 5 stripes parity information evenly across all the disks. If one disk fails, the data can be reconstructed from the parity data on the remaining disks.
RAID 6 is also known as RAID 5 with dual parity. In RAID 6, data is written across all disks as in RAID 5, but two sets of parity data is calculated. Performance is slightly decreased compared with RAID 5 because the extra parity data must be calculated and written to disk. RAID 6 allows for recovery from the failure of up to two drives in the array with the help of dual parity (RAID 5 allows for recovery using the parity data if only one drive in the array fails).
RAID 10 is a combination of RAID 0 and RAID 1, and requires a minimum of four disks. First, two sets of disks are organized in RAID 0 arrays, and devices are then mirrored. Hence we get the speed advantages of RAID 0 with the data redundancy associated with mirroring.