Well, the disadvantage of using an internal HD for backup is that it doesn't get to rest, thermally. It's always in the same hot case as the original, and if it's spinning most of the time, it's more likely to fail.
But, internal drives are usually faster, and these things don't break that often.
So, kind of a trade-off. Certainly you can put a Safety Clone on it without worry...
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--Dave Nanian
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