Overview
First, one or more data files are analyzed and a group of 'parity files' are built that record the structure of the files to be protected.
Later, if any of the protected files are lost, the parity files can be used to re-create the missing files.
Even if one or more of the parity files are missing, the remainder of the set can still rebuild missing original files, if there is enough of the backup present. If too many files are missing, the parity files will not have enough base data to work with.
Read more about this topic: Parity File