RAID LEVEL 2: Hamming Code ECC

 

Each bit of data word is written to a data disk drive (4 in this example: 0 to 3). Each data word has its Hamming Code ECC word recorded on the ECC disks. On Read, the ECC code verifies correct data or corrects single disk errors.

Characteristics & Advantages

  • "On the fly" data error correction
  • Extremely high data transfer rates possible
  • The higher the data transfer rate required, the better the ratio of data disks to ECC disks
  • Relatively simple controller design compared to RAID levels 3,4 & 5

Disadvantages

  • Very high ratio of ECC disks to data disks with smaller word sizes - inefficient
  • Entry level cost vey high - requires very high transfer rate requirement to justify
  • Transaction rate is equal to that of a single disk at best (with spindle synchronization)
  • No commercial implementations exist / not commercially viable

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