When you notice that your samba throughput is not what it should be, it might be related to the mount options in your Linux client ( mount command ).

When mounting my Samba share with the following command ( on a gigabit link ):

mount -t smbfs -o username=verwilst //10.0.10.10/data /mnt/smb/

I got these results:

time cp /tmp/blob-1.5G /mnt/smb/blob-1.5G-smbfs

real    4m46.677s
user    0m1.512s
sys    0m27.862s

When the share is mounting with this command:

mount -t cifs -o username=verwilst //10.0.10.10/data /mnt/smb/

The copy command gives us this:

time cp /tmp/blob-1.5G /mnt/smb/blob-1.5G-cifs

real    0m18.050s
user    0m0.028s
sys    0m5.828s

Quite a difference you get by replacing 1 word eh ;)