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I copied a 3.5GB file from my SATA HD to my Seagate USB 2.0 external HD in about 3 minutes.
I copied the same 3.5GB file from my SATA HD to my USB 2.0 SanDisk Cruzer and it took more than 15 minutes.

What possible reason could there be for such a gross difference?
Slackware 13.37 full install, single user machine, nothing else going on during either copy.

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migrated from stackoverflow.com Nov 10 '11 at 20:57

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2 Answers

These are two entirely different kinds of devices! One is a hard drive, and the other is flash. Of course you're going to have different write performance.

USB is not exactly the limiting factor in speed here.

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Interesting, I had assumed that if a device describes itself as "USB 2.0" then it would be able to handle data transfer speeds up to the limit for "USB 2.0". What you seem to be saying is that "USB 2.0" means nothing more than "somewhat faster than USB 1.1". –  user985675 Nov 10 '11 at 16:48
    
@user985675, No, I'm saying that the interface to the computer is completely and totally separate to the speed of the storage in use. If I talked 250 words per minute, you would be able to hear me, but wouldn't be able to write down what I said. Of course the device's USB interface can handle speeds up to the maximum spec of USB 2.0, but that doesn't mean its processor and storage can handle it. Your assumptions about reality, and what I said, couldn't be much farther from the truth. –  Brad Nov 10 '11 at 18:06
    
I also assume you did not literally mean what you said in the last sentence of your previous comment, that you would have preferred to write "Your assumptions about reality and what I said, couldn't be much farther from the truth." The comma you added after "reality" quite changes the meaning of the clause immediately following. If you read the two sentences, without what I am beginning to assume is your customary contemptuous impatience, you might appreciate the difference. Otherwise, thank you for the information you have provided. –  user985675 Nov 10 '11 at 19:54
    
Even between flash you have big differences. The number of channels, the speed of the controller, the speed of the flash memory itself. Typically cheaper drives are slower. Article comparing USB 2.0 flash drive benchmarks –  Bert Apr 10 '13 at 13:48
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You can check the write speed for the two devices.

Some data for Sandisk Cruzer flash drives suggests write speed in the range of 4 to 10 MB/s

Seagate say a SATA disk can transfer data at a burst rate of 300 MB/s. Obviously, this may be constrained by the limit in USB 2 of 60 MB/s for "hi-speed". SUstained speed will be lower than 300 anyway.

All the above are affected by many other factors.

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