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[Discuss] USB speeds

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Just ran a test on my system with no BS specified (eg 512) and BS=1MB
4:22.87elapsed using the default, 1:49.50elapsed using BS=1MB

On 08/29/2011 03:12 PM, Jerry Feldman wrote:
> On 08/29/2011 03:05 PM, Rich Pieri wrote:
> > Two factors come immediately to mind, neither of which have anything to
> do with the bus.
> > On Unix, file systems are mounted asynchronously by default. I've seen
> this cause horrible performance degradation on USB flash media. Try
> mounting sync instead.
> > You neglected to specify a block size so dd defaults to 512 byte
> blocks. This is horribly inefficient. Try powers of 2 starting at 1MB to
> find an optimal value.
> When I use dd to copy an image I make sure that the device is not
> mounted. Note that I am copying to the device.
> I think that when I copied the image, I did use bs=1MB. As I mentioned,
> I will plan to run a benchmark test tomorrow in my office if all my
> servers come up ok.
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> Discuss mailing list
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Jerry Feldman <gaf at>
Boston Linux and Unix
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