Level 5 employs a combination of striping
and parity checking. The use of parity
checking provides redundancy without the
overhead of having to double disk capacity.
Simply put, parity checking involves
determining whether each given block has an
odd or even value. These values are summed
across the stripe sets to obtain a parity
value. With this parity value, the contents
of a failed drive can easily be determined
and rebuilt on a spare drive.