Gigabit Samba

[Dag]

I'm trying to run Samba on a gigabit network.
On the server side I've got Samba 2.2.1 running on an sgi Origin200 with a 
gigabit ethernet card plugged into a gigabit switch, and the files are being 
served off a fibrechannel raid array.  On the client side I have a windows 2k 
box with a gigabit card plugged into the same switch.  Both machines and the 
switch claim that everything is running at 1Gb/s, yet file transfere doesn't 
seem any faster than with fast ethernet.  

Is samba simply not able to serve up files at gigabit speeds or is there some 
tweaking that needs doing to get it to do this, or is it simply some problem 
with my network?

Dag