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Some experiment I did with hard drive read/write speed was 10MB/s write and 40MB/s read, and with a USB Flash drive, it can be 5MB/s write and 10MB/s read.

Also, if I put a virtual hard drive .vhd file in a hard drive or in a USB Flash drive and try a Virtual Machine using it, the one using the hard drive is quite fast, while the one using the USB Flash drive is close to not usable.

So I wonder some early netbooks use 4GB or 8GB flash memory as the hard drive, and even the Apple Mac Air has an option of using flash memory instead of a hard drive. But in those situation, will the speed be slower than using a hard drive, like in the case of a USB Flash drive?

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Hook your hard drive up through a USB port and run your tests again. –  Tester101 Nov 3 '09 at 15:57
    
Do you have USB 1.x or USB 2.0 ports? –  rob Mar 18 '10 at 20:33
    
@Jian: did any of the answers answer your question, or was there something more you were looking for? –  rob Apr 17 '10 at 0:34

3 Answers 3

up vote 7 down vote accepted

One big difference is that the flash drive is using the USB bus, while the drive is using the SATA bus. So even if your flash memory was the same speed in both cases, the drive would have a higher potential throughput.

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This only explains Jian's performance discrepancy if the computer only has USB 1.1. USB 2.0 allows for up to 60 MB/s. The problem, in this case, is more likely that the Jian's flash memory is inherently slow. SSDs usually use faster flash memory and/or more advanced configurations such as interleaving in order to achieve higher performance. –  rob Mar 18 '10 at 20:41

In your case it depends on your USB-port specification (2.0 is much faster, but 1.0 is very slow) and USB-port of your drive. And in case of netbooks they have a fast SSD drives. 'Tis very-very fast.

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I thought the flash drives used in netbooks were all low performing models that only outpaced magnetic HD's in seek time, but still fell behind in transfer speeds. I know SATA ones you can buy aftermarket are much faster than anything else on the consumer market. –  Dan Neely Mar 18 '10 at 20:40

As others have pointed out, it depends on the speed of the bus, but for your measured speeds the bus is probably not the bottleneck (assuming you're using USB 2.0). The maximum throughput of USB 2.0 is 480Mbps (60 MB/s).

Flash memory write speeds can vary widely, depending on the particular technology used. Typically, USB flash drives are extremely slow because of the memory type and internal configuration. SSD drives usually address the performance discrepancy by interleaving the memory modules.

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