RAID

Raid stands for Redundant Array of Inexpensive Disks, now called Redundant Array of Independent Disks

This technology allows for the combining of multiple disks into a single logical unit. Data is written or read from the logical unit across all of the drives. How this is done is dependent on the RAID level that is used.

Here are the basic RAID levels which are standardized by the SNIA (Storage Networking Industry Association) in the Common RAID Disk Data Format (DDF) which is currently in version 2.0:

  • RAID-0: Striped array with no parity
  • RAID-1: Mirrored array
  • RAID-3: Striped array with non-rotating parity, optimized for long, single threaded transfers
  • RAID-4: Striped array with non-rotating parity, optimized for short, multi threaded transfers
  • RAID-5: Striped array with rotating parity, optimized for short, multi-threaded transfers
  • RAID-6: Similar to RAID-5 but with dual rotating parity, tolerating two physical disk failures

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