Earlier today I had a discussion with a colleague on possible ways to store (ISO) images of CD-ROMs and DVDs in our repository system. In addition to checksums, he suggested to also generate and store parity data for each image file (e.g. using the par2 tool: http://manpages.ubuntu.com/manpages/trusty/man1/par2.1.html). This would enable one to repair files in case of bit-level corruption.
This made me wonder how commonly parity info is used in digital archives, and if there are any best (or at least recommended) practices. E.g. what levels of redundancy are typically used? I'm not really familiar with this at all, and it's not a subject that is often mentioned in digital preservation discussions (but see https://twitter.com/anjacks0n/status/733281959762395139).