On Fri, Apr 15, 2011 at 4:57 PM, Michael Watterson <mike@radioway.org> wrot=
e:
> On 15/04/2011 09:17, Xiaofan Chen wrote:
>> On the other hand, even though I have bought two
>> USB 3.0 external hard disks, none of my PCs
>> come with USB 3.0 host controller (XHCI)
>
> For Random Access, an HD might just beat USB 1.1
>
> Only bursts to or from the on-board controller cache can exhaust the
> speed of USB 2.0 on a single drive.
>
> Drives are natively faster toward edge of platter. Native block transfer
> sequential speed (excluding track to track stepping or random access) is
> limited by rotational speed and bit density. For larger transfers, even
> without Random Access, the track to track delay is very high.
>
> USB 2 is worthwhile. I'm sceptical that USB 3.0 is needed for ordinary
> single drives.

Just look at a simple benchmark comparison here.
http://www.notebookreview.com/default.asp?newsID=3D5761&p=3D2

Or more comprehensive result here.
http://www.tomshardware.com/charts/usb-3.0-storage-charts/benchmarks-2,108.=
html

Then you will understand why USB 3.0 is necessary.

--=20
Xiaofan
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