I just installed a new 3TB Book on a 2.0 USB computer. The transfer rate is below 15MB/sec. Any other USB drive using the same port produces way over 30MB/sec for the same content. What is wrong here?
Test the drive on a different cable
check the drive for problems with a test software like drive sentinel
You may also try different USB ports, and another computer, in order to compare results. Do you receive good transfer rates by USB 3.0?