Try doing a search on Microsoft for "EnableTcpChimney" - if this is not enabled you could see poor performance.

At a command promt run the "netstat -nt" command and see if the 10Gb connection is listed as "offloaded"

Lastly, make sure there are sufficient disks in the raid group to handle the IO load that you're trying to test.

For delayed ACK see Knowledgebase article emc150702:

On a server that runs Windows Server 2003 SP1 or later or Windows  2008, follow these steps:

1. Start Registry Editor (Regedit.exe).
2. Locate and then click the following registry  subkey:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces
   
   the  interfaces will be listed underneath by automatically generated GUIDs like  {064A622F-850B-4C97-96B3-0F0E99162E56}
3. Click each of the interface GUIDs and perform the following steps: 
   
   a.  Check the IPAddress or DhcpIPAddress parameters to determine whether  the interface is used for iSCSI traffic.  If not, skip to the next interface. 
   
   b.  On the Edit menu, point to New, and then click DWORD  value.
   
   c.  Name the new value TcpAckFrequency, and assign it a value of  1.
4. Exit the Registry Editor.
5. Restart Windows for this change to take effect.

glen