Thomas, your answer makes the assumption that a hacker will have access to the entire harddrive, which
could happen, but it's much more likely that the hacker will only have access to
either the SQL server
or the web server, which is why I specifically mentioned that best practice is to host them separately. Statistically, the most likely attack vector is the SQL database, so let's start there: Assume the hacker has downloaded all your hashed passwords and their associated salts. Those salts are meaningless at that point. That is why you need a 2nd salt known only by the web app. —
Lakey 10 mins ago