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USB 3 - Real World Performance?

Holy Stating the Obvious Batman - USB 3 is quicker - who knew?


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I’ve been resisting upgrading my late 2011 Macbook Pro due to the lack of a 17” unit in the current range - and I love the 17” screen on my ‘Pro! I’m resigned to having to go with the 15” though - and pressure is building for the upgrade.

Anyways, one of the reasons to upgrade for me is the access to USB 3 ports, as my current unit only has USB 2. USB 2 has been around since the turn of the Century (!), and has a maximum signalling rate of 480Mbit/s - which is an effective throughput of about 35MB/s. USB 3 however - introduced in late 2008 I think - has a signalling rate of 5Gbit/s…which is obviously tons faster.

I tend to work with a lot of VMWare images, and these can be multi-gigabyte. The ones I’m utilising at the minute for example are around 60Gb each. Pushing these to an external drive can be painfully slow. Also, a drive connected via USB 2 isn’t fast enough really for me to run the machines from those drives - they may be fast enough for some, but not for me…So I end up dragging them to my internal drives. In fact it’s probably the primary reason I’ve removed my DVD drive and fitted a second hard disk - so I have a 500Gb SSD, and a 750Gb physical drive in my laptop.

I was curious however to see what the real world differences on USB 3 would make though - could I realistically use the speed of an SSD in an external USB 3 caddy to speed up moves of machines, and also as a place to
run the virtual machines from? So I’ve done a small test - video below - showing the real world differences between the two. For the test, I’ve used a Crucial M4 256Gb SSD, connected via USB 2 on my Macbook Pro, and then USB 3 on a 2012 iMac. The test is the copy of a 2.1Gb Aperture Library. It’s a fairly rudimentary test and doesn’t take into account different file sizes etc. but it does show the general performance gap between the two standards.

Copying to the external SSD via USB 2 took 74 seconds, which is 26.9MB/s.
Copying to the external SSD via USB
3 took 14 seconds, which is 142.3MB/s.

So, quite a bit faster then - about 5 times quicker. Certainly fast enough to run Virtual machines natively from the USB 3 hosted drive anyway, and it’ll speed up copying loads. For example a 60Gb VMWare image would take about 7 minutes on USB 3, and about 38 minutes on USB 2 - that’s a massive difference.

Anyways, you can see the video below.



After producing that initial video, I was asked to compare a normal physical (Non-SSD) drive between a USB 2 & USB connection - so I’ve done that too. Again, video is below. In this test I copied a 3.37Gb ISO image to the drive - times below:

Copying to the external spinning drive via USB 2 took 127 seconds, which is 27.2MB/s
Copying to the external spinning drive via USB
3 took 45 seconds, which is 76.7MB/s

So the USB 2 time is about the same, which goes to show that the performance restrictor is the interface, not the drive. The USB 3 time is about 2.8 times quicker - so again, quick significant. On that, you’re obviously running in to the performance limit of the drive as the throughput figures are very similar to the drive I have connected internal over SATA.

See the video below for more info.



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