RAID Levels: Redundant Array of Independent Disks

Standard RAID levels comprise of configurations that employ the techniques of
* STRIPING
* MIRRORING
* PARITY
to create large reliable data stores using general purpose HDDs.

Levels are standardized by SNIA (Storage Networking Industry Association) in Common RAID Disk Drive Format (DDF)

RAID 0 >> STRIPING (No fail-over, No Redundancy, Total loss of information if disk fails, each disk size will be of smallest disk size in the set of the disks)
RAID 1 and its variants >> MIRRORING (Copy of write will be in more than one disk, Redundancy, less performant)
RAID 5 >> Distributed PARITY
RAID 6 >> Dual PARITY

Source: Wikipedia

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