1. RAID Redundant Array of Inexpensive Disks

2. History Single Large Expensive Disk (SLED) Single Large Expensive Disk (SLED) IBM and Berkeley University IBM and Berkeley University RAID levels 0-5 RAID levels 0-5

3. Why RAID? Redundancy, fault tolerance Redundancy, fault tolerance Increased capacity Increased capacity Increased performance Increased performance

4. Mirroring The easiest way to get high availability The easiest way to get high availability Half the size Half the size Higher read performance Higher read performance

5. Striping Higher performance Higher performance Distributed across disks Distributed across disks Work in parallel Work in parallel

6. Parity Improve the availability Improve the availability Less waste of space Less waste of space

7. RAID 0 Striping Striping Highest performance Highest performance Lower availability Lower availability

8. RAID 1 Mirroring Mirroring High availability High availability Low computing power Low computing power

9. RAID 2, 3, 4 Parity Parity High performance High performance High availability High availability

10. RAID 5 Parity with distribution Parity with distribution Higher performance than level 1-4 Higher performance than level 1-4 High availability High availability Most used RAID level Most used RAID level

11. Combinations of different levels Combine two levels and get the advantages from both Combine two levels and get the advantages from both Either hardware driven, software driven or a combination of both Either hardware driven, software driven or a combination of both Examples: 0+1, 1+0, 0+3, 3+0, 0+5, 5+0, 1+5, and 5+1. Examples: 0+1, 1+0, 0+3, 3+0, 0+5, 5+0, 1+5, and 5+1.

12. Alternatives to RAID Single Large Expensive Disk (SLED) Single Large Expensive Disk (SLED) Redundant Array of Distributed Disks (RADD) Redundant Array of Distributed Disks (RADD) More alternatives: 2D-RADD, C-RAID, RO WB-optimistic and RO WB-pessimistic More alternatives: 2D-RADD, C-RAID, RO WB-optimistic and RO WB-pessimistic

13. The End First RAID system. Second RAID system.