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What is RAID

RAID is a system for grouping disks in order to reduce the risk of data loss in the event of a disk failure. RAID is not a substitute for backup and should not be treated as such.

RAID Levels

The RAID array is divided into several levels, each with different advantages and disadvantages:

  • RAID0: The simplest level that allows the full capacity of all disks to be used. The minimum number of disks for this level is 2. The disadvantage is that it provides no data protection against disk failure.
  • RAID1: The most common level where the data on one disk is copied to the other. This way, if one disk fails, the data is still available on the second one. The minimum number of disks for this level is 2. The disadvantage is that half the total capacity of the two disks is lost.
  • RAID5: A level where a checksum of the data across disks is maintained. The minimum number of disks here is 3. The disadvantage is that this level slows down write operations due to the generation of the checksum.
  • RAID6: A level where the checksum is stored on two disks. This allows for up to 2 disk failures in a minimum array of 4 disks. There is again a slowdown due to checksum generation.