Re: Slow downloads: NSLU2

[David Fokkema <dfokkema@ileos.nl>]

On Thu, 2007-05-31 at 09:38 -0400, Lennart Sorensen wrote:
> On Thu, May 31, 2007 at 11:23:03AM +0200, David Fokkema wrote:
> > I know. However, it would be nice to get around 30 Mb/s, which is less
> > than 10% of it. When I 'dd', I get around 7 Mb/s with CPU at ~ 80% which
> > is almost entirely spent as 'system'. I used:
> > 
> > dd if=/dev/zero of=test.bin bs=1024 count=102400
> > 
> > (I just did the test)
> > 
> > Do you see the same figures? Why is so much time spent as 'system'? I
> > would've understood if it was 'wait' or something like that... Don't we
> > have DMA?
> 
> Remember USB is measured in bits per second not bytes per second, so
> 480Mbit/s generally only gets about 22MB/s even on a very high end PC due
> to whatever overhead is involved in USB.  Firewire seems to be able to
> get much closer to its theoretical limits while using a lot less CPU
> too.

Ouch! I'll grab my disk and check its speed on my 'high-end' laptop to
see what it gives me.

Thanks,

David