left USB port(900mA)=3.0 and right USB port(500mA)=2.0
If you go to "Apple logo>about this mac>sytem report>hardware>USB" you'll see that left USB port has 900mA = 3.0 USB and the right USB port is only 500mA = 2.0 USB...
This is why we are having problems reading external hard drives in the right USB port.
In the apple website under "macbook pro>performance" it says there "two USB 3 ports". -_-"
MacBook Pro (Retina, 13-inch, Mid 2014), OS X Yosemite (10.10.3)