[Samba] vista client poor transfer rates

[ken]

Hi

I am running samba 3.0.25c on a fc6 server.
The problem is I am getting poor transfer rates to a vista client, 
approx 8Mb/sec over 1Gb Ethernet compared to 40Mb/sec to the same 
machine dual boot machine running xp pro.
I am using more or less default settings with the exception of
vfs objects = readahead set in each file share.
I am also getting about 40Mb/sec when transferring from vista to samba.
It does not appear to make any difference if the vfs objects = readahead
option is set or not, is there any way to confirm it is operating
correctly or is there anything else that would cause this anomaly.

Thanks