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I've tried these cables on PCs, and found that they are NOT hot swappable. Unless the Mac Pro has a different SATA implementation, which I doubt, since it's an Intel board.

However, that enclosure claims it's hot swappable. In such a case, I would suspect as long as the enclosure isn't disconnected from the MP, you should be fine. Just make sure it's on and plugged in before you boot.
 
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