tuning parameters for parallel access to umass devices?

[Doug White]

On Tue, 23 Sep 2003, Brian Behlendorf wrote:

> > 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.

Well with the copy, its consuming all the available b/w to the device. Not
much we can do about that without hurting I/O performance.

> > > 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.

Well duh ... firewire is 400Mbit, USB is 10Mbit :-)

Not likely that thi sis an easy fix.  It'd involve redoing the way I/O is
scheduled to a device (*_strategy).

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