USB 3.0 slower than SATA for SSD

I have a Kingston V200 256GB SSD. When connected to my SATA 6.0gbps port on my motherboard I'm seeing sequential read speeds of 300 megabytes / second.

When I put the drive into a sata to USB 3.0 enclosure and connect it to my USB 3.0 motherboard port my sequential read speed is maximum of 200 megabytes / second and average of 120 megabytes / second. I tried the enclosure on another machine and got 120 megabytes / second as well.

I'm guessing the enclosure itself is the bottleneck. Anyone know of reviews/benchmarks on enclosure chipsets themselves so I can buy something that isn't going to slow me down?

Answer

http://electronicdesign.com/article/embedded/whats-difference-usb-uasp-bot-73593

The enclosure lacks the faster UASP mode. Real world throughput of USB 3.0 has a maximum of 400MB/sec (USB 3.0 has 36% overhead in the best case scenario).

Typical USB 3.0 devices seem to be only BOTS enabled limiting them to a maximum of 250MB/sec although in my case this seems to be a slower drive enclosure.

eSata 3.0gbps is still faster than USB 3.0 in the average case at 300MB/sec real world. Disappointing.

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