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  1. 1. RAID Redundant Arrays Of Independent Disks Group : 3 Miss Munni Unmul Habbiba (dc2013MCA00) Keyilamswabe (dc2013MCA00) Bikash dhal (dc2013MCA0028)
  2. 2. Introduction :
  3. 3. Solution: RAID  Technology that employs the simultaneous use of two or more hard disk drives to achieve greater levels of performance & reliability.  Several physical disks are set up to use RAID technology, they are said to be in a RAID array.  This array distributes data across several disks, but the array is seen by the computer user and operating system as one single disk.
  4. 4. Different Levels of RAID  RAID Level 0  RAID Level 1  RAID Level 2  RAID Level 3  RAID Level 4  RAID Level 5  RAID Level 6
  5. 5. Figure : RAID Level 0 (Striping)
  6. 6. RAID Level 0  Requires a minimum of 2 drives to implement.  The first byte of the file is sent to the first drive, then the second to second drive and so on.  Striping is the segmentation of logically sequential data, such as a single file, so that segments can be assigned to multiple physical devices
  7. 7. RAID Level 0  Advantages:  I/o performance is greatly improved by spreading the i/o load across many channels & drives.  Best performance is achieved when data is striped across multiple controllers with only one drive per controller.  Disadvantages:  It is not a “True” RAID because it is NOT fault-tolerant. The failure of just one drive will result in all data in an array being lost.
  8. 8. Figure : RAID Level 1 (Mirroring)
  9. 9. RAID Level 1 Data duplicated, also the controller card Requires only two drives to implement  Duplicate copies of data, so if a disk fails, data is still available and applications keep running. Advantages Better than single disk Simple to Implement Disadvantage - high check disk overhead.
  10. 10. Figure : RAID Level 2
  11. 11. RAID Level 2 Uses Bit-level striping with Hamming codes of ECC. Disks are synchronized and striped in very small stripes, often in single bytes/words. Hamming codes error correction is calculated across corresponding bits on disks, and is stored on multiple parity disks. Advantages Good read and write performance Disadvantages: High overhead for check disks Not used in modern systems
  12. 12. RAID Level 3
  13. 13. RAID Level 3 Uses dedicated parity disk. Requires a minimum of 3 drives to implement. Every write requires updation in parity data . Advantages improved performance and fault tolerance. Disadvantages:  One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.
  14. 14. Figure : RAID Level 4
  15. 15. RAID Level 4 Uses Block-level striping with dedicated parity Requires minimum of 3 drives to implement Each disk operates independently which allows I/O requests to be performed in parallel. Advantages Read Performance is very good because of the blocks. Lowest overhead of check disks. Disadvantages Quite complex controller design Not commonly used
  16. 16. Figure : RAID Level 5
  17. 17. RAID Level 5 Uses Block-level striping with distributed parity Requires a minimum of 3 drives to implement Advantages Read performance very good. Lowest overhead of check disks. Disadvantages Most complex controller design. Difficult to rebuild in the event of a disk failure.
  18. 18. Figure : RAID Level 6
  19. 19. RAID Level 6  Raid Level 6 uses Block-level striping with dual distributed parity. Advantages: Continues to operate with up to two failed drives. Disadvantages Most complex controller design. Difficult to rebuild in the event of multiple disk failure.
  20. 20. THANK YOU