John Galea's Blog

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USB 3 Vs USB 2 for hard drives

I work in an area with a bunch of tekkies, ok geeks. They are a great bunch of guys with a great deal of intelligence around the table. Now before any of you get too swelled a head, I’m not talking about you. I’m talking about the other guys 🙂 We have some lively and educational conversations over lunch etc. Well some of the time anyway. Other times we digress into standard guy stuff. Sometimes this leaves me scratching my head wondering about a particular topic. Now your wondering is there a point to this current seemingly meaningless blog post. Why yes there is! The topic came up is there any difference between connecting a USB hard drive by a USB 2 and 3 port. I must say my answer was that there is not a difference because the rotating media is the limitation not the bus.

So onto the test. Now first off I had some difficulty getting a reliable number off my old tried and true drive benchmark called Checker. So I gave up on that and used two things to measure the speed difference. First of all I used a straight Windows copy (which of course is doing a read from the USB drive and a write to the local drive). The second thing I did was to use Checker and timed how long it took to copy the entire file space (without writing it anywhere). This was to remove any delay from writing and focus entirely on the USB bus. I used a directory with 8.9G of MP4 movies. So they are large files that are heavily compressed, and should largely be sequential reads. This should remove some drive head latency issues from getting in the way of the USB bus speeds.

First off I was shocked to see the variation in speed on the USB 3 bus. I don’t have any explanation for it. Check out this graph from Windows. The speed varied from a peak of around 80MB/s to 30MB/s.
usb-3

I didn’t capture the graph but on USB 2 it was a steady approx 30MB/s.

So let’s do the numbers. To copy the files took 263 seconds on USB 2 Vs 185 on USB 3 meaning USB 3 was 42% faster. In bandwidth the numbers are an average of 46MB/s on USB 3 and 32 MB/s on USB 2.

The numbers become even more pronounced when you remove the write operation and just do a read. USB 3 took 105 seconds Vs 260 seconds on USB 2 meaning USB 3 was a whopping 148% faster than USB 2. In bandwidth the numbers are an average of 81 MB/s for USB 3 Vs 33 MB/s for USB 2.

Wow was I ever wrong. USB 3 is indeed significantly faster. You were right John! 🙂 We learned in engineering don’t let what you (think you) know get in the way of what you don’t know. I’m glad I did the test. I am now enlightened!

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February 1, 2014 - Posted by | Uncategorized

1 Comment »

  1. Goodbye WiFi and wireless devices if you try to use USB3 — Intel’s OWN report here — http://www.intel.com/content/www/us/en/io/universal-serial-bus/usb3-frequency-interference-paper.html

    Comment by William | May 14, 2014 | Reply


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