simultaneous copy to multiple media

[Claudio Grondi]

I don't know any deep details about USB, except that
I _know_ that it is a serial bus, but considering
following:

1) I can read/write 45 MByte/s from harddrive to harddrive
on the E-IDE bus (theoretically 100 MByte/s), so the
speed of the harddrive I read/write from/to is probably the
bottleneck.
2) if I understand it right, an USB controller is connected to
to the PCI bus and there can be many separate USB
controller on one PC
3) the theoreticall speed of USB (430 MByte/s?) is much
higher as the experienced 15 MByte/s, probably due to slow
controller on the side of the external storage media, so
maybe even on one USB line I will have the chance to
use it full capacity connecting many slow devices
(I can't imagine, that USB goes down with the speed to
the speed of the slowest component connected, does it?)
4) with 45 MByte/s I could theoretically simultaneously
supply three separate data streams to three USB
controller writing with 15 MByte/s each out to the
external storage media.
5) watching the low CPU usage while writing to USB
shows me, that CPU-time is not a problem.

I still see a chance of writing truly simultaneously to
several devices connected via USB.
Please let me know if I am wrong in any of the
points (1-5) or if my conclusion is based on
wrong assumptions or if I use a wrong way of
infering.

By the way: I was not thought about bus design at
university, so what I know about it is comes from
self-study :-).

Claudio
P.S. Your message appears in my Outlook Express
as one having no content, but an attachment, so I can't
read it directly.

> Is there maybe a way to use a direct DMA
> transfer to multiple target destinations
> (I copy to drives connected via USB ports) ?
Think about what USB stands for. Then reconsider whether you'll ever have
the
chance of writing truly simultaneously to several devices connected via
USB... And then, as an extra exercise, think about why it takes so long when
several different jobs are done in parallel, writing to devices connected
via
USB.
Bus design... Don't they teach anything at uni these days? ;)
-- 
--- Heiko.