M-Disc with another M-Disc copy stored off-site. Basically, the only way to get 100% instead of 99.9999% for the next 100 years.

RAID is for uptime or speed, not for this. It also comes with the dubious feature that you can
lose
your
data
once more
without any disk failures

This question has been asked many times. Have multiple copies, replace bad copies with copies. That’s it.

raid but just for one file

Google “quickpar”, it’s exactly this.

If it’s really, really important I would probably RAR it with a larger % of recovery records, then use PAR files against it, then store it in many, many places. And every once in a while copy it to new places, checking the PAR files for checksum errors.

Use PAR files like the others suggested.

Or use WinRAR’s recovery volumes.

While the par file suggestions are the most reasonable thing to do there are some more interesting alternatives.

Try horcrux. It’ll split your file into several pieces and make it so you only need a few of the pieces to recreate your file. You could make 99 pieces and only require 3 of them to reassemble. That way if most of them are damaged somehow you can still recreate your file.

This is similar to how Storj splits your files into 80 pieces and only needs 29 to recreate your data. It is also similar to how satellites transmit data when part of the message can be lost in transmission.

Print out the binary code and scan it using OCR later on. Store that in a fireproof safe (/s but would work)

Write it down an sealed in vacuum.

Many copies in many places, with some of the places being as far away as possible - a different country at least, a different continent even better.

Par files are a good start, but if you want a truly resilient archive, you need to actively manage it. You need multiple copies in multiple places that you check on a regular schedule.

If it’s that important, I’d have multiple copies on multiple media, in multiple geographic locations. Like two hard drives and a flash drive, as well as the tape. And in multiple formats. Like raw, and rar’d.

My point is, anything important, you shouldn’t have only one copy of it. The more important it is, the more copies in separate locations you should have.

Lzip is another nice format for this, I don’t know how it compares to PAR though.

May help to get you down that rabbit hole for further research: https://www.newsgroupreviews.com/par-files.html

This might be a dumb question, but can you print it?