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I'm running a Linux system, so I'm asking a solution that can run on Linux, better if via terminal on a command line.

I have a laptop with an integrated SD card reader, which is connected to motherboard via USB. I just wanted to test its maximum speed, as it is surely not near to unlimited like some completely native card readers like cameras' ones. I mean, if I buy an SD faster than my reader, to use only in my PC, it would be a waste of money, right? Is my speed determined by USB maximums? Or is it a way to test its potential maximum speed without having to buy a secure digital faster than it just to see when it caps? And if it is USB standards dependent, how can I know if it is USB 2.0 or 3.0 connected?

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I can't imagine it's slower than USB2, and I don't believe that you can get many SD cards fast enough to saturate USB2. UHS-1 cards which are just recently coming out support something like 50-100MB/s maximum, which could saturate it, but those are few and far between.

I can't think of a way to test it without a suitably fast card.

As for seeing if it is USB2 or USB3, you should be able to use lsusb. Run it. See what bus the reader is on, then look at the top to see if that is a 3.0 bus or 2.0 bus.

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Thanks. Running lsusb I get some devices with specific names (among them, my wireless cards and other I don't understand) and three USB 2.0 hub with one 3.0. Given that I have a 3.0 and two 2.0 ports, I guess it is a 2.0 connected reader. But isn't USB 2.0 effective speed capped to 35 MB/s? SanDisk "Extreme" cards are guaranteed with a 45 MB/s speed, nevermind "Extreme Pro" with their 95. Is 35 MB/s enough fast for using the card by installing an operating system to it? –  HisDudeness Dec 8 '12 at 8:07
    
Theoretically it caps at 60MB/s, but realistically around 45. That ought to be fast enough for an OS, considering a typical hard drive is at best twice that fast. I'd be more worried about longevity. Cheap flash tends to fail pretty quickly when used as an OS drive. –  ssmy Dec 10 '12 at 15:15

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