A slow HDD won’t offer much more than what a USB 2.0 can offer so that’s not that good. This gets down to the ability of the storage medium to either send the data or accept it. If we have the same pressure across all of the interfaces there are conditions which the water (data flow) won’t offer much difference. Now while I’ve been discussing throughput we also need to think about that other element the water pressure in our model. Of course the Thunderbolt is the biggest and the USB 2.0 is the least. Think of water which is under the pressure which pipe will off more water using the throughput numbers I just gave you as their diameter. So now let’s use a model which is a better way of looking at this. The last external interface your system has is a Thunderbolt (first generation) port which offers 10 Gbps of thoughtput.

This gets into speed of the USB interface of your system yours is only a USB 2.0 (480 Mb/s) Vs the faster USB 3.0 (640 Mb/s) then you have the older FireWire 800 interface which offers (800 Mb/s) theoretical throughput. While USB drives have their place for data storage they are not overly fast even a SSD drive.

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