To test the USB 3.0 ports on the Defiance III, I plugged in an OCZ Trion 150 SSD via a SATA-to-USB 3.0 5Gbps adapter, which uses the ASMedia ASM1053 controller. We reviewed the SSD HERE, finding it delivers good speed at a budget price.
Most importantly, it is capable of saturating the USB 3.0 bus, allowing us to test the speeds the USB 3.0 ports deliver. To test this, I ran both CrystalDiskMark and ATTO Disk Benchmark on the Trion 150 drive.
As you would expect, the results are right at the ceiling of the USB interface. There are also 2x USB 3.1 Type-C ports on the Defiance – but unfortunately I had nothing on hand capable of saturating the USB 3.1 bus.