Redundant Arrays Of Independent Disks


Published on

Published in: Technology
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Redundant Arrays Of Independent Disks

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