On Fri, 2011-04-15 at 09:57 +0100, Michael Watterson wrote:
> 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)
>=20
> For Random Access, an HD might just beat USB 1.1
>=20
> Only bursts to or from the on-board controller cache can exhaust the=20
> speed of USB 2.0 on a single drive.
>=20
> Drives are natively faster toward edge of platter. Native block transfer=
=20
> sequential speed (excluding track to track stepping or random access) is=
=20
> limited by rotational speed and bit density. For larger transfers, even=20
> without Random Access, the track to track delay is very high.
>=20
> USB 2 is worthwhile. I'm sceptical that USB 3.0 is needed for ordinary=20
> single drives.

I'm not sure why you say that.

Pretty much ANY modern drive will EASILY saturate a USB2 connection. The
fastest most people can transfer over USB2.0 is about 30MBps, it's been
a while since a hard drive was that slow.

I regularly transfer many GBs of data over a USB2 connection (an
external USB harddrive for offsite backups), I can't wait for USB3 to be
more common.

TTYL


--=20
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