1. RAID
Redundant Arrays Of
Independent Disks
Group : 3
Miss Munni Unmul Habbiba (dc2013MCA00)
Keyilamswabe (dc2013MCA00)
Bikash dhal (dc2013MCA0028)

2. Introduction :

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. 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. Figure : RAID Level 0 (Striping)

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. 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. Figure : RAID Level 1 (Mirroring)

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. Figure : RAID Level 2

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. RAID Level 3

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. Figure : RAID Level 4

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. Figure : RAID Level 5

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. Figure : RAID Level 6

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. THANK YOU