Because Duplicati has almost no requirements for the backend (only requirements are get, put, list and delete operations), the only way to test the integrity of backed up volumes is to re-download some random files to check if the contents can be read and verify if everything looks as expected.
You can set the number of files to download after a backup with --backup-test-samples=n. replace n with the number of files you want to download for verification. Use option --no-backend-verification=true to disable downloading test samples completely.
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