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I am burning some DVDs and BDs with important data and, in addition to replication, I am adding parity data using PAR2 tools.

However, as additional safety, I would like to place the parity files on the outer end of the burned optical media, corresponding to the most delicate part of the discs. This way the probability of having damages to the rest of the files is lower. Another option would be the opposite: placing parity files at the inner end, since they can repair any file and are therefore highly valuable. In any case, I need to be able to choose their layout on disk.

Is there a way to do that? Either a specific software or a trick to generate images with existing software.

I tried years ago Nero Burning ROM, but it is a Windows-only tool. I tried standard mkisofs or similar tools but they don't provide this feature.

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Use your DVD writing software to create a multi-session DVD. Write your parity files in the first session, then in the next session, the data. This will put your parity files close to the hole. I am not aware how to enforce ordering in an ISO image.

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Consider adding all of your files to a tar file and then burn the tar file to your disc.

Say you are standing in the directory with your files and your parity data, and that your files are:

  • Photos/
  • Videos/
  • Documents/
  • example.wav
  • hello.c
  • hello.h

and you have parity files named with a .par2 extension

then if you run

tar cvf ../burnme.tar *.par2 hello.c hello.h example.wav \ Photos/ Videos/ Documents/

it will add the par2 files at the start, followed by the files hello.c, hello.h, example.wav and the directories Photos/, Videos/ and Documents/. The order of the files under each directory will be as returned by your OS (i.e. readdir on Linux) but if you care about the exact order you can use a pattern for example to add each file in order instead of adding the whole directory. However I am assuming that since your question is only about putting the tar files relative to the others, that's all we care about here.

Do NOT compress the tar file, because if you do then a single or just a few bit errors might destroy your data, depending on the compression algorithm used, and also compressed data must be decompressed in order to be accessed and so adds overhead.

By itself, tar is simply a container and it will be possible to read individual files without almost any overhead at all.

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    If you do this, you no longer have your files on the disc. Instead, you have a .tar file there. And a .tar file needs extra software for extraction. – user477799 Mar 23 '17 at 19:13

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