Low perfomance when read from usb flash drive

[M. Warner Losh]

In message: <200903010038.29534.hselasky at c2i.net>
            Hans Petter Selasky <hselasky at c2i.net> writes:
: On Saturday 28 February 2009, Artyom Mirgorodsky wrote:
: > Read speed when copy from usb flash drive decreased from 20MB/s (old usb
: > stack) to 12MB/s. (on windows above 22Mb/s).
: >
: 
: Hi please explain what kind of test you have done. It's most likely not 
: related to USB, but rather the file system.
: 
: Maybe you can run the following test on Windows and FreeBSD to compare:
: 
: dd if=/dev/da0 of=/dev/null bs=65536

I've done a lot of data movement with usb1 and usb2 (love those .dv
videos of youth hockey).  This is exactly opposite of the results that
I'd typically see through the filesystem (ufs).  For usb1 I'd see
about 15MB/s and for usb2 I'd see between 16MB/s and 18MB/s.  Since
this is all ufs, no windows numbers are available for comparison.
These are the numbers reported by gstat, so it includes all the
filesystem traffic.

So a drop from 20MB/s to 12MB/s would be somewhat out of my range of
experience...

Warner