How can I archive files to blueray with redundancy?

Question

Reading recently about facebook's usage/desire to use blu-ray disks for long term cold-storage, I wonder if this might be an additional mechanism to backup my photos and videos.

The part that worries me is the potential for a disk to go bad.

Is there software that will enable me to save with redundancy similar to RAID5/6?

In other words, I would

• create a tar 4*(capacity of blu-ray
• save it on 5 disks
• if one of the 5 fails, the other 4 have enough information to recover.

EDIT - solution Based on Christopher's answer (thank you):

tar -czf - <the files> | split -b 500m - foo.tar.

which gives foo.tar.aa, foo.tar.ab,...

par2 c -r26 -- basename foo.tar.*

note that it's very important to give the basename. I initially did this:

par2 c -r26 -- foo.tar.* # don't do this

It didn't consider one of the four files of my test and it wasn't able to recover after I removed one of them. It's unfortunate that such a mistake can be made. Easy to do it right and hard to do it wrong. Not in this case.

In any case, I think it will work.

Answer 1

A very simple example is to take your first 200GB* of files (4 BD-50s) and zip the entire group into 500MB archives.

Then generate 25% par2 files for those zip archives. So now you burn 200GB zip files to four discs and 50GB par2 to the fifth disc. You can extract the original 200GB dataset with any 4 discs.