freebsd stable - Sep 2003 - tuning parameters for parallel access to umass devices?

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:

da2 at umass-sim0 bus 0 target 0 lun 0
da2: <Maxtor 5000XT v01.00.00 0100> Fixed Direct Access SCSI-0 device
da2: 650KB/s transfers
da2: 239371MB (490232832 512 byte sectors: 64H 32S/T 42763C)

Though I've seen it with other umass devices, like my digital camera and
the Archos jukebox.

While copying a large file (or large number of files), and in parallel
attempting to do a "ls" of a directory or read a file, one waits a
significant amount of time.  Is there a way to tune the disk, mount
options, kernel sysctls, something, to make file I/O over USB less
blocking?

	Brian

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?
> 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.

-- 
Doug White                    |  FreeBSD: The Power to Serve
dwhite@gumbysoft.com          |  www.FreeBSD.org