A variety of disk-organization techniques, collectively called redundant arrays of expensive disks(RAIDs) are commonly used to address performance and reliability issues. RAID composed of small, cheap disks were viewed as a cost-effective alternative to large, expensive disks. RAID concepts have been extended to tape drives, and for broadcasting of data.  RAID Levels  Level 0 - refers to disk arrays with striping at the level of clocks but without any redundancy.  Level 1 - RAID level 1 refers to disk mirroring.  Level 2 – this level is another level of RIAD 2, which is a very high level of standard data transfer. This level uses bit-level stripping and every bit stored in different hardware.  Level 3 – This RAID level, helps you to transfer a very high amount of data and it also provides high efficiency.  Level 4 -  this level, contains block-level data stripping. It is also another unpopular level of RAID 4.  Level 5 – RAID level 5, ensures you create security and integrity of data stored on the hard disks . Level 6 - RAID level 6, is a data storage level, that lets you combine four or more hard drives into single logical hard drives. It also boost the system to work fast.