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.
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.
Comments
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.
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.