Surely it&#x27;s OK for a backup drive to fail occasionally. Your working drive might fail occasionally too but it&#x27;s extremely unlikely that both of them fail within a day or so of each other. That&#x27;s the situation that would lead to loss of data.<p>That&#x27;s for a pure backup. For a history of previous versions, of course you&#x27;d want more reliability if you only have one copy of that history.