tuning parameters for parallel access to umass devices?

[Brian Behlendorf]

On Tue, 23 Sep 2003, Doug White wrote:
> On Mon, 22 Sep 2003, Brian Behlendorf wrote:
>
> > It looks like copying files over USB to a umass device causes other I/O
> > attempts to be blocked for an unreasonable (10-20 seconds) amount of time.
> > Here's the device in question:
>
> On the volume being copied to, or another volume?

On the volume being copied to (or from) - that is, while moving a big file
to/from such a device, doing an 'ls' or other operations on that device
are delayed.

> > da2: 650KB/s transfers
>
> Don't forget that this isn't much faster than a floppy disk, and flash I/O
> is pretty slow anyway.

Granted.  This is do a hard drive that can definitely handle it - mounting
the same drive (Maxtor 5000XT) over firewire works brilliantly - the
full 50MB/s transfer speed, and parallel operations are fine.  I just
don't have fw everywhere.

	Brian