Redundant Array of Independent Disk (RAID)

RAID is a technology which uses two or more disk for storage,reliability,availability,fault tolerance. They can have a disk range from minimum of 2 to maximum of 32.Raid are of several level of RAID based on the specifications and configurations.RAID 0 writes data on striped volume,it writes the data into small chunks across all the volume.Reading and writing on RAID 0 devices is faster.However striped volumes are not fault tolerant,that means if one disk fail it would be impossible to recover the data stored on the volumes.RAID 1 is also known as disk duplexing,there is no striping of data,read performance is better since data can be read from any of the disk and it also fault tolerant.RAID 2 is rarely used ,it writes the the across the disk with parity error information.RAID 3 dedicates one disk to store the parity information for data recovery in case of disk failure.RAID 4 writes data in blocks with dedicated parity.RAID 5 uses block level striping with distributed parity,which can be used to regenerate the data in case of disk failure.Usually RAID devices use SCSI interface with multi-pins to connect to server.