Re: bkbits.net is down

David Brownell
2003-06-29T03:16:33Z

> From: Alan Cox
> Date: 2003-06-28 23:13:55
>
> On Sad, 2003-06-28 at 23:15, Dr. David Alan Gilbert wrote:
> > Hmm - why should it suck so badly? Shouldn't USB 2 (yes I mean the
> > 480Mbps) manage 40MByte/s+ ?

Custom devices certainly have done that, with drivers that keep
everything busy. Last fall, one person reported 38+ MB/sec
from a VT8235. The theoretical peak bandwidth for bulk traffic
(what most folk want) is 52 MByte/sec.

A Western Digital drive I tried gave me 27 MByte/sec with USB.
And I hate to say that the FireWire mode didn't work at all,
since I was curious how they'd compare! (2.5.71 or so.)

> I don't think you get the full 480Mbit/sec on a single device.
> 5Mbyte/sec is a bit low

Some combinations of EHCI silicon, USB-to-IDE adapter, and IDE
work better than others ... I once switched a drive from one
EHCI controller to another (same host and OS, didn't reboot),
and went from 5 MB/s to 19 MB/sec. That was on 2.4; with the
2.5 usb-storage, both controllers gave the higher speed.

> but that may be some of the remaining work on
> the USB EHCI drivers. I've not tried 2.5.x which may be way better here.

The key difference in 2.5 is that usb-storage queues requests,
no more slow page-at-a-time I/O. It's the same EHCI driver
underneath, lately -- much improved since last September (or so)
when it first started to generate real user feedback.

- Dave