Lecture on RAID

Introduction to RAID

• Definition: RAID (Redundant Array of Inexpensive/Independent Disks)
• Purpose: Prevent data loss by using multiple hard drives
• Benefits:
  • Improved data security
  • Enhanced performance and reliability

Data Striping

• Concept: Technique of splitting data across multiple hard drives
• Benefits:
  • Faster read/write operations
• Levels:
  • Bit Level
  • Byte Level
  • Block Level (group of bytes)

RAID Levels

RAID Level 0

• Technique: Block Level Data Striping
• Fault Tolerance: None (Data loss if one drive fails)
• Performance: Fastest
• Storage Space: 100% utilization (e.g., 2x50GB drives = 100GB)

RAID Level 1

• Technique: Mirroring (Copying data to another drive)
• Fault Tolerance: High (Data preserved if one drive fails)
• Performance: 50% (Duplicated work)
• Storage Space: 50% utilization (e.g., 2x50GB drives = 50GB usable)

RAID Level 2

• Technique: Bit Level Striping with Parity
• Details:
  • Splitting bits of each byte across multiple disks
  • Extra disks for storing parity information
• Usage: Rarely used

RAID Level 3

• Technique: Byte Level Striping with Parity
• Details:
  • Extra disk for storing parity information
  • Parity helps restore failed disk (Not parity drive)

RAID Level 4

• Technique: Block Level Striping with Parity
• Details:
  • One disk for parity storage
  • Parity helps restore failed disk (Not parity drive)

RAID Level 5

• Technique: Block Level Distributed Parity
• Details:
  • Parity distributed among several disks
  • Can handle one disk failure
  • Storage Space: 75% utilization

RAID Level 6

• Technique: Block Level with Double Distributed Parity
• Details:
  • Double parity bits distributed among several disks
  • Can handle failure of two hard disks
  • Widely used by big companies (e.g., Google, Facebook)

Conclusion

• Key Points: Various RAID levels provide different benefits and trade-offs between performance, fault tolerance, and storage efficiency.
• Levels Overview:
  • RAID 0: Block Level Striping
  • RAID 1: Mirroring
  • RAID 2: Bit Level Striping with Parity
  • RAID 3: Byte Level Striping with Parity
  • RAID 4: Block Level Striping with Parity
  • RAID 5: Block Level Distributed Parity
  • RAID 6: Block Level Double Distributed Parity

End of Lecture