My tests were done on an expensive Dell XPS desktop where one would assume that the setup is optimal. But as you can see from the measurement results, eSata is faster than USB3. The enclosures I used are both from Rosewill.To obtain full USB 3 performance everything in the chain must be of good quality and designed for USB 3.
Thanks to all.
All what you said makes a lot sense.
Have a wonderful new year.
e-SATA is rated for up to 6Gbps; USB 3.0 is only up to 5Gbps. Keep in mind those are only maximum figures and machines could have slower speeds. PCI-e x1 is only 5 Gbps so a card with, say, four SATA 3.0 ports but runs off of only one PCI-e lane hasn't a prayer for full speed if more than one USB 3.0 port is in use at the same time. Yet USB 3.0 cards that run on more than one PCI-e lane are rare as honest politicians.
I have a related question. The USB cables which came with portable drives (USB3) are quite short. (18 inches). I ordered a few 6ft USB 3.0 extension cables to connect with the short USB 3.0. I wonder the use of extension cable would degrade the speed or not.
Possibly, if the cables are poor quality. Generally, six feet add to 18" should not be a problem.
Don't forget that there's an order of magnitude difference in bandwidth between USB 2.0 and USB 3.0. The reason USB 3.0 cables are shorter and thicker than the former, is for additional screening and to preserve that bandwidth during transfer of data between two external devices.
I would return those longer cables and move external devices closer to source port.
For USB 2 the maximum cable length is about 16 feet. USB 3 doesn't specify a length limit but no more than 10 feet (3 meters) is recommended. But cable quality is more important then length. A cheap cable 6 feet long could limit speed.
See this for more information:
USB Cable Length Limitations And How To Break Them
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