I wanted to buy a drive that can perform faster than 5 Gb/sec. This USB 3.1 gen 2 device does just that.
I've tested this in macOS Sierra. The Apple drivers in Mac OS X El Capitan do not support 10 Gb/sec.
I've connected this device to a AlpineRidge Thunderbolt 3 controller. No issues there.
I've connected this to a ASMedia 1142 PCIe card from Startech. Half the time, System Information.app would say the speed was "Up to 480 Mb/sec". When this happened, the drive performed at USB 2.0 speeds. The other times, it says "Up to 5 Gb/sec" but the benchmarks I tried showed that it was doing more than 5 Gb/sec. Windows 10 had similar issues, but would sometimes show the connection as 10 Gb/sec. I tried two different USB-C cables (one was a Thunderbolt 3 cable). This may be an issue with the ASMedia chip in general, my PCIe card specifically, Apple's XHCI driver, or a combination. I only have one PCIe card and this one USB 3.1 Gen 2 device to test.
I used Black Magic Disk Speed Test.app to test the speed. This will get you some quick ballpark numbers:
USB 2.0 speed: 41.5 MB/s Write, 41.8 MB/s Read USB 3.0 speed: 411.2 MB/s Write, 428.0 MB/s Read USB 3.1 Asmedia 1142: 710.1 MB/s Write, 784.3 MB/s Read USB 3.1 AlpineRidge: 756.3 MB/s Write, 836.5 MB/s Read
Those numbers were from a Skylake PC (4.6 GHz). The USB 3.1 speed was slightly slower in a Mac Pro 2008 using the Asmedia 1142 PCIe card: 660.3 MB/s Write, 740.5 MB/s.
For the SSD's, I used two 1.0TB Mercury Extreme Pro 6G.