RAID

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RAID

• Redundant Array of Inexpensive Disks

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History

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

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Why RAID?

• Redundancy, fault tolerance
• Increased capacity
• Increased performance

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Mirroring

• The easiest way to get high availability
• Half the size
• Higher read performance

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Striping

• Higher performance
• Distributed across disks
• Work in parallel

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Parity

• Improve the availability
• Less waste of space

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RAID 0

• Striping
• Highest performance
• Lower availability

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RAID 1

• Mirroring
• High availability
• Low computing power

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RAID 2, 3, 4

• Parity
• High performance
• High availability

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RAID 5

• Parity with distribution
• Higher performance than level 1-4
• High availability
• Most used RAID level

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Combinations of different levels

• Combine two levels and get the advantages from
  both
• Either hardware driven, software driven or a
  combination of both
• Examples 01, 10, 03, 30, 05, 50, 15, and
  51.

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Alternatives to RAID

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

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The End
Second RAID system.
First RAID system.