How many External Hard Drives can I plug to Airport Extreme? I need to backup all my computer data. I'm thinking of buying 3 External Hard Drives and connect them to Airport Extreme. Can I do this?
The constraint is be the number of ports available on your USB hub.

Any connected hard drives should appear in Mac OS X. 
Use a self-powered usb hub and connect hard drives your hub. Only then will multiple external drives have enough power to run.

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