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by wereHamster 2564 days ago
Whether recovery leads to (almost) useable data depends on what byte you modify. It's entirely possible that a single corrupt byte in the compressed data leads to a single corrupt byte when uncompressed. When you are dealing with images you may not even notice that a single pixel is wrong. But it's also possible that you completely destroy the data such that the decompression algorithm can't even deal with it and has to give up.
1 comments

A decade and a half ago, I wrote an Oracle archived log that I had compressed with bzip2 to a DLT40 tape.

I recovered and uncompressed (without error) the log, then tried to apply it to a database recovery which rejected it as corrupt.

After several attempts to read the tape (amounting to dozens of hours), I finally put it in the original drive that wrote it and pulled the file to the remote recovery system - this worked.

I immediately began including PAR2 files on the tapes, so the restored contents could be verified and corrected.

I have my doubts that bzip2 is as sensitive to corruption as the author of asserts, but perhaps there have been improvements to the code since my misfortune.