I used a Hitachi HTS541612J9SA00 5400RPM 120 GB SATA (2.5") hard drive as HDD1 and I used a Hitachi Deskstar HDS728080PLA380 7200RPM 80 GB SATA (3.5") drive as HDD2 (note I did not pre-format or erase data from the destination drive). I inserted both hard drives in the appropriate slots (HDD1 and HDD2; but it doesn't really matter) and pressed the power button. It takes a few seconds to power up and recognize both drives (the blue led indicator lights will flicker when you transfer files to and from the drives).

I used HD Tune Pro to test the data transfer rates of both drives and below are the results that I got :

So basically both drives read at around an average transfer rate between 16.5 MB/s and 16.8 MB/s. Random access times averaged between 14.7 ms to 17.6 ms. Both of these tests showed that these transfers do use up a lot of CPU resources, but this wouldn't be the case if we used the eSATA connection. Unfortunately, I was not able to test using eSATA because my test system did not have an eSATA port.