USB 2.0 and 3.0 in the real world

USB 2.0 and 3.0 in the real world

Summary: USB 3.0 devices are common now, but how much benefit do they really give over 2.0?

TOPICS: Hardware

One of the things I was looking forward to for quite a long time was USB 3.0 peripherals, especially flash memory sticks: I read and write USB sticks so frequently as part of trying out new Linux distributions that I really get tired of waiting on those things. 

However, now that USB 3.0 devices have become pretty common (and the price has come down on them somewhat), and I own two netbooks with USB 3.0 ports, I slowly began to realize that the difference in speed that I am seeing in my everyday use is not that much. So I decided to investigate this a bit further, and do some simple testing to determine how USB 2.0 and 3.0 compares in my actual use.

To perform these tests, I have used my Acer Aspire One 725 and my HP Pavilion dm1-4310ez. Both of these netbooks have one USB 3.0 port and two USB 2.0 ports, so I could try reading and writing both 2.0 and 3.0 on the same systems. 

I was running openSuSE 12.3 with the latest updates and patches applied on both systems. I used four different USB 3.0 flash memory sticks; a Philips 8GB USB 3.0 flash drive, a disk2go 8GB USB 3.0 flash drive, a Verbatim 16GB USB 3.0 flash drive, and a SanDisk Extreme 16GB USB 3.0 flash drive. The SanDisk was the only one which actually advertised its read/write speeds on the commercial packaging, the other three drives only said "USB 3.0 SuperSpeed" or something similar.

In running these tests I found that I had to be very careful to ensure that the computer was not reading/writing to/from cache rather than to/from the USB device itself. This became obvious when I was timing a read from the USB drive which took something like 50 seconds the first time I did it, and about 10 seconds the second time.  Duh. What I ended up doing was ejecting the flash drive after each read or write test, thus forcing Linux to discard whatever cached data it might have for the device.

I wanted to use a large enough data file to ensure that I got reasonable and consistent timing results. I had a copy of the latest Slackware ISO image that I had recently downloaded, and it is something like 2.4GB in size, so I decided to use that. All I did was copy the file between the netbook hard drive and whatever flash drive I was testing.

The final detail of the preparations - how to determine how the computer sees the flash drive. The Linux lsusb -v command gives complete details about all USB ports and any currently plugged devices. 

First find the specific device being tested - each section starts with a header describing the device, but you still have to read carefully because the name listed here (and thus the company who made the guts of the device) is often not the same as the name on the case of the device. 

Buried in the details about each of device is the value "bcdUSB", which can be 2.00, 2.10 or 3.00 (or 1.00 if you happen to have some very old sticks). The 2.00 and 3.00 values are obvious, and as far as I can tell the 2.10 value is what it reports when a USB 3.0 device is plugged into a USB 2.0 port.  If someone knows more details about that, feel free to add a comment.

The first step was to copy the file from my Swiss Army Flash Drive to the laptop disk. This flash drive is USB 2.0, so that will also give me a sort of a baseline reference to compare to the USB 3.0 devices.  I copied it twice, ejecting the drive in between copies, and it took 1:48 the first time and 1:46 the second time.

I then ejected that drive and set it aside, and tested each of the USB 3.0 drives using the same procedure.  First, plug the drive into a USB 3.0 port and confirm (with lsusb -v) that has been recognized as a USB 3.0 device. Then copy the 2.4GB file from the hard drive to the flash drive. 

Then delete the file from the flash drive, and unmount, unplug, replug and remount the device. Then copy the file to it again. The delete the file, unplug the flash drive, and plug it back in but this time on one of the USB 2.0 ports. Check that it is recognized as a USB 2.10 device, then repeat the previous copy/delete/eject/plug/copy procedure to get USB 2.0 write times.

Ok, so much for the methods.  Hold onto your hat, here are the results that I got when testing on the Acer Aspire One 725:

AO725 USB 3.0 Read USB 3.0 Write USB 2.0 Read USB 2.0 Write
Philips 0:55 / 0:54 11:28 / 11:19 1:20 / 1:20 11:30 / 11:45
disk2go 0:50 / 0:50 4:55 / 4:49 1:20 / 1:20 5:07 / 4:53
Verbatim 0:47 / 0:47 3:27 / 3:30 1:30 / 1:28 4:14 / 4:08
SanDisk 0:30 / 0:29 0:46 / 0:44 1:17 / 1:23 1:22 / 1:21

 Ok, that's pretty interesting.  It certainly shows that there can be a lot of variation between different USB 3.0 flash drives. Then I repeated the entire procedure, this time using my HP Pavilion dm1-4310ez netbook.  The results were:

dm1-4310 USB 3.0 Read USB 3.0 Write USB 2.0 Read USB 2.0 Write
Philips 0:54 / 0:53 11:56 / 11:47 1:19 / 1:17 11:26 / 11:58
disk2go 0:47 / 0:48 5:58 / 6:10 1:17 / 1:19 7:21 / 7:14
verbatim 0:46 / 0:47 3:39 / 3:55 1:28 / 1:28 5:03 / 5:02
SanDisk 0:18 / 0:16 0:44 / 0:44 1:16 / 1:17 1:22 / 1:19

I have to admit that some of this surprised me.  I expected that there would be a difference between the various USB 3.0 sticks from different manufacturers, but I didn't expect the difference to be this large.

As a final test, because of the way that I frequently use USB sticks (to boot Live images of various Linux distributions), I decided to time how long that took as well. I didn't bother with trying each of the four sticks listed above, since I think the comparative results are pretty clear. 

I used only the fastest one (the SanDisk), and then I tried it in USB 3.0 and 2.0 ports. I was a bit surprised by the results - on my HP dm1-4310, it took about 45 seconds to boot Fedora 20 (Gnome) with the stick in the USB 3.0 port, and almost exactly the same with it in the USB 2.0 port. 

I tried this twice to be sure, and it was consistent. I'm not entirely sure what this means, but I suspect that it is related to the fact that when you first boot, the firmware loads some minimal drivers to support common peripherals and the USB driver that it uses only does 2.0, not 3.0 so there is no difference in booting from the different ports.

Oh, and also for comparison to "normal" boot, this is the system which has an SSD hard drive installed, and in normal use it boots Fedora 20 in less than 15 seconds.

The moral of the story is that you really should pay attention to what you are buying when you look for a USB 3.0 stick.  It is not a simple case of "you get what you pay for", because all USB 3.0 sticks are not equal in performance, and some USB 3.0 sticks are not any better than 2.0 sticks.  If price is your primary selection criteria, then don't be surprised if you get a 3.0 stick that is not much better than a good USB 2.0 stick - and in fact, if price is really your only criteria, you can almost certainly get a better price/performance ratio in a USB 2.0 stick.  But if you are willing to spend a bit more to get better performance, then you really need to look closer before you buy.

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Topic: Hardware

J.A. Watson

About J.A. Watson

I started working with what we called "analog computers" in aircraft maintenance with the United States Air Force in 1970. After finishing military service and returning to university, I was introduced to microprocessors and machine language programming on Intel 4040 processors. After that I also worked on, operated and programmed Digital Equipment Corporation PDP-8, PDP-11 (/45 and /70) and VAX minicomputers. I was involved with the first wave of Unix-based microcomputers, in the early '80s. I have been working in software development, operation, installation and support since then.

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  • I/O or flash memory test?

    Sorry if I missed this, but these were all flash drives (aka thumb drives) - yes? If so, then seems like a test of the flash read/write speed more than the USB I/O speed.

    I know a USB 3.0 hard drive is MUCH faster than my USB 3.0 flash drive.
    Bruce Lang
    • Correct, sorry

      You are correct, they were all flash drives, and thus the post should have been titled "USB 2.0/3.0 Flash Memory Drives".

      Thanks for reading and commenting, and pointing this out.

      • Not surprising

        When you buy flash chips to embed in devices they come in a large variety of speeds. From slowest to fastest they can vary by a factor of 1000. That was a couple of years ago and I do not know what the variation is today. I have always wondered how to tell what you were buying since such a small number of brands provide this spec.

        I suspect the same is true of the new solid state disks. You probably have to watch speeds much more closely than capacity if you expect to get the benefits of solid state disks.

        In general I have given up on flash drives and do everything off of SkyDrive now. Any cloud would be fine. Most of the time it is faster than a flash drive even with poor Wi-Fi connections.
  • Re: USB 2.0 and 3.0 in the real world....

    Well for me at least the speed difference is stark. Running OS X Mavericks from a USB 3.0 External Drive SSD is lightning fast and more than acceptable performance from OS X Mountain Lion with an USB 3.0 External HDD.

    I did try running OS X from a USB 2.0 External Drive but performance was poor due to the low transfer rate. So for me at least USB 3.0 is a major plus.

    I do still use older External USB 2.0 Drives for storage.
    • Re: USB 2.0 and 3.0 in the real world....

      Hardware Specifics :

      Crucial M4 512GB SSD in USB 3.0 Caddy running OS X Mavericks.

      LaCie 500GB HDD Porsche Design USB 3.0 running OS X Mountain Lion.
  • .....

    My reaction after wasting my time reading that article was "duh!". It has been obvious to anyone paying attention that USB flash drives have varied greatly in speed ever since the first flash drive came in to existence.

    Also, and you didn't even bother to test this, the difference between read and write times can vary massively between various drives. A drive can be read very quickly but write times can be painful.

    The bottom line is if you care about performance you should never buy a flash drive that doesn't list read and write speeds. The manufacturers fudge on those ratings too but they are usually close enough to compare different drives.

    Also, pay attention to read and write speeds. Some manufacturers will play up a huge read speed but the write speed is just awful compared to other drives with a lower read speed.
    • Perhaps read more carefully?

      I'm sorry you felt that you wasted your time, but perhaps you should have wasted a bit more, and read it more carefully? There are columns in the tables for "Read", and columns in the tables for "Write", isn't that exactly what you are saying I "didn't even bother to test"? You are correct, those two values can vary greatly, as is shown in the tables for the Philips drive, which had read performance not much worse than the other three, but write was much worse - as much as twice as long.

      Thanks for reading and commenting.

      • Re: A waste of Time.

        I'm afraid that I also feel, either correctly or incorrectly, that this article wasn't as conclusive as it might have been.
        I read a lot of things being conveyed as facts, to do with read/ write speeds, which was instantly followed by a debunking.
        -Something about how speeds vary massively between drives.
        Although this information is very(!) useful and not really a waste of time, it does make me wonder: How do we know that these results are fair, accurate and, "In the real World", when presumably if there are slower USB. Flash Drives, there are sure to be faster ones as well.

        I wonder if this was the complaint being made.
        In3D Limited
    • Since the first flash drive

      You'd need at least two flash drives to compare speed :-)

      I'd like to see speed difference between that fast Sandisk flash drive and a USB 3.0 HDD.
  • Really, you didn't expect a large variation?

    Just take a quick look at the range of specs listed on any website selling USB drives. You have to CLOSELY pay attention to the read/write rates, AND read reviews validating these rates.

    You should shop for USB thumb drives the same way you shop for SSDs. Look at the same specs, and you will be happy. Buy a no-name or even name-brand POS USB thumbdrive, and you may as well be transferring at 1.1 rates.
    • Variation Expected, but not so large

      Hmmm. Well, I did expect significant variation, but I don't think that I expected any of the USB 3.0 speeds to be worse than the USB 2.0 speeds. I still find that one a bit shocking.

      Thanks for reading and commenting.

  • drivers?

    Have you also considered that the drivers you are using could be a factor? Your Philips drive shows usb2 and usb3 performance as nearly the same. Maybe their USB3 driver is really a marginally tweaked USB2 driver. The Sandisk has a much wider gap, which might be attributed to a better USB3 driver.

    When VAXen started getting faster serial ports, many of my customers did not even know about setting baud rates, so they saw no performance increase at first. I think the ports were set to 9600 (maybe even 1200) by default for backward compatibility and had to be manually reconfigured to use the higher baud rates available. If the authors of the USB3 drivers focused on backward compatibility rather than optimizing throughput that could explain at least part of the performance variance. I'd be interested in seeing a similar test with different drivers, perhaps even different platforms - other Linux distros or other operating systems - to see if that changes the results.
    • From the story:

      "...I suspect that it is related to the fact that when you first boot, the firmware loads some minimal drivers to support common peripherals and the USB driver that it uses only does 2.0, not 3.0 so there is no difference in booting from the different ports."
      • @Bill4 re:drivers

        that makes perfect sense for the boot tests, but the first two rounds of testing involved copying files after booting, so the optimal drivers should have been installed, rather than the more generic drivers loaded from firmware. I spend most of my time in Windows, and have seen marked improvement in some devices when replacing the driver that shipped with Windows is replaced by a device-specific driver from the manufacturer.

        He also did not mention the model numbers for the USB drives tested. A quick glance at NewEgg shows USB3.0 flash drives with manufacturer specs from 80/12MB/s R/W (Adata Model AS102P-8G-RGY) to 450/445MB/s R/W on a Mushkin Model MKNUFDVU240GB. A test with several drives with the same specs would be of interest.

        Without knowing the claimed spec for the drive the only real info here is that different drives perform differently. Where's the comparison of "vendor claimed performance" vs "actual performance"? "The SanDisk was the only one which actually advertised its read/write speeds on the commercial packaging, the other three drives only said "USB 3.0 SuperSpeed" or something similar." Then you should have looked up the specs on the manufacturer's website, Mr Watson, or at least provided the model numbers.
  • Wait... seriously?

    You're doing USB speed comparisons using USB Keys? On Linux? And this is 'real world'.. how?

    USB keys don't just have non-standard performance across keys - they often have different performance between uses!

    This would have been a far, far more meaningful test if you'd taken two drive cases (preferably made by the same manufacturer), one USB 2 and one USB 3 and a 1TB HD and put the same drive into each one and ran the tests.
  • Windows 2 Go

    I typically will run sessions using Windows 2 Go on a USB 3 and the speeds are rather good. Of course MS allows (officially) only 3 thumb drives and all of these are optimized to run full Windows via a USB port.
    Rann Xeroxx
  • USB 2 will go the way of USB 1, which is no longer remembered.

    Just as rechargeable batteries are rated for their capacity in milliamperes, USB Flash Memory devices come in different speeds and it the difference varies. With difference models of the same brand, the same is true.
  • This is a joke. Right?

    Maybe you need to have some real testing done. First, the memory in USB keys can differ the same way as memory in a system - or for that matter a SSD drive.
    I have both USB2 and USB3 ports on my system [my mobo was one of the first to have USB3 ports about 4 years ago]. I notice the difference between USB2 and USB3 when transferring to and from them. They may not get the actual theoretical maximum speed [but I'm sure almost none do].
    Drivers are a fact as well. So is the chipset. Some chipsets are using clones or inferior hardware [recall BTW, that apple didn't want to use Samsung based WiFi chips and took cheaper clones and had some issues with them for stability].
  • USB 2.0-3.0

    Real world results: Transcend 64 gig 3.0 transferring 10 gigs running mint 16 resulted in transfer speed (write) of 78.6 mps.

    Same 10 gig using HP 32 gig 2.0 resulted in transfer rate (write) of 21.3 mps.

    Significant difference. I'll take 3.0 over 2.0 anyday.
  • All Data Can Be Valuable

    Cheers for an interesting article JA.
    I think a couple of you are giving him an unnecessarily hard time over the methodology! You can poke holes in any approach; at least this one provides reasonable consistancy between 'sticks'.
    It also reinforces my prejudices from using digital cameras where I have found that SanDisk memory provides the best bang per buck.
    Kev Baylis