Really helpful! The answer is as you say: the HDD was not getting enough power because both the connectors were power connectors and it was getting an uneven amount of power. The back-feeding to the pi was a red herring. I bought a four-point unpowered USB hub which had an extra USB dongle for power...

Hello all, So, I'm in the same boat of trying to get a 2.5inch HDD working with the Pi and a USB router. I salvaged the HDD from an old Samsung netbook, and bought a cheap-as USB / SATA cable which has two USB ports on it - one for the data and the other for extra power. I also bought a 10w 2 port U...