Briefly define the seven RAID levels.

8. 0: Non-redundant  
   
   1: Mirrored; every disk has a mirror disk containing the same data.  
   
   2: Redundant via Hamming code; an error-correcting code is calculated across corresponding bits on each data disk, and the bits of the code are stored in the corresponding bit positions on multiple parity disks.  
   
   3: Bit-interleaved parity; similar to level 2 but instead of an error-correcting code, a simple parity bit is computed for the set of individual bits in the same position on all of the data disks.  
   
   4: Block-interleaved parity; a bit-by-bit parity strip is calculated across corresponding strips on each data disk, and the parity bits are stored in the corresponding strip on the parity disk.
   
    5: Block-interleaved distributed parity; similar to level 4 but distributes the parity strips across all disks.  
   
   6: Block- interleaved dual distributed parity; two different parity calculations are carried out and stored in separate blocks on different disks.