Re: USB 2.0 with 250Gb disk and insane loads

[David Brownell <david-b@pacbell.net>]

Alexander Hoogerhuis wrote:
> 
> I had a private reply form a guy that had three of these running
> reliably on 2.4.21-pre6, and he noted he'd never done cd->disk
> transfers, but across the net. So I did the same.
> 
> Results are that it survived a lot longer, I managed to get about
> 700Mb across at about 8Mb/s (line speed 100mbit half duplex) before it
> fell over with this:
> 
> ...
> usb-storage: Command WRITE_10 (10 bytes)
> usb-storage:  2a 00 18 f0 34 47 00 04 00 00
> usb-storage: Bulk command S 0x43425355 T 0xc43 Trg 0 LUN 0 L 524288 F 0 CL 10
> usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes
> usb-storage: Status code 0; transferred 31/31
> usb-storage: -- transfer complete
> usb-storage: Bulk command transfer result=0


> usb-storage: usb_stor_bulk_transfer_sglist: xfer 524288 bytes, 128 entries
> usb-storage: Status code 0; transferred 524288/524288
> usb-storage: -- transfer complete
> usb-storage: Bulk data transfer result 0x0

That's two successive operations on the OUT endpoint
(two IRQs:  request, then 128 pages) both of which
worked fine, followed by one on the IN endpoint:


> usb-storage: Attempting to get CSW...
> usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes
> usb-storage: usb_storage_command_abort called
> usb-storage: usb_stor_stop_transport called
> usb-storage: -- cancelling URB
> usb-storage: Status code -104; transferred 0/13
> usb-storage: -- transfer cancelled
> usb-storage: Bulk status result = 3
> usb-storage: -- command was aborted
> ...

Interesting.  So basically, the failure mode you saw
was that after all the data was (evidently) transferred
OK, usb-storage aborted (for some reason) its fetch
for the transfer status ... and then trouble.

Why did usb-storage abort that IN transfer?  If we
knew that, we'd have a good clue as to what's going
wrong.


> Load only got up to about 3-4 before it fell over.
> 
> Apart from that, it seems the speed at which it falls over is depening
> on two factors: with/without debugging and speed at which data arrives
> for the drive.

Not unrelated.  Turning on usb-storage debug slows down the
rate at which data is handed to the drive.

- Dave