![]() However it is pretty short and doesn't tell what the different parts really do. The 7z SDK contains a file format description ( a copy of which can be found online here). I dug a bit deeper, and 7z stores CRC-32 checksums for files in the archive. I don't count corruption to the archive metadata, as that is obvious when 7z won't open the archive. 7z archives, and are they sufficient to detect file corruption? I couldn't find the part responsible for the test action. I also had a glance at the source code, but I didn't understand where to look for. I had a look at the 7z format specification, which seems to include places for CRC checksums of some kind. Unfortunately that's all help and documentation say about it. Running "7z -h" describes it as "Test integrity of archive". I discovered that 7z has the "t" action to "Test archive files". Reading the file again is pretty slow though. This is necessary because 7z seeks while creating a 7z archive so I can't its output through a pipe. Currently the archive is written to an external HDD and then read again for checksumming. I store checksums next to the archive file to detect file corruption. ![]() I chose 7z because it has easy to use desktop apps for Windows and Linux, in case I need to recover the data quickly. I recently started using uncompressed, encrypted 7z archives for backups.
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