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2 - System resilience, High Availability, and Fault Tolerance - Coggle…

- - - - Use two or more disks and improves the disk subsystem performance, but does not provide fault tolerance
    - - Use two disks, which both hold the same data.
    - - Three or more disks with the equivalent of one disk holding parity information. Allow the reconstruction of data if one disk is lost.
    - - Four or more disks with the equivalent of two disk holding parity information. Allow the reconstruction of data if two disks are lost.
    - - Use at least four disks and continue to operate as long as at least one drive in each mirror continues to function
  - - - Manual recovery
        
        Not failing in a secure state
      - Automated recovery
        
        Able to restore itself against at least one type of failure
      - Automated recovery without undue loss
        
        Able to restore itself against at least one type of failure + specific objects are protected to prevent their loss (e.g. restore corrupted files, rebuild date from transaction logs, verify integrity of key systems)
      - Function recovery
        
        Able to automatically recover specific functions