Sorry NickC_UK It would be 0-7 on SAS A and 8-15 on SAS B.  
I understand that the Perc 310 has two SAS controller connectors, each of which has four ports.  However I cannot fin out how these relate to actual disk slots in the backplane. We will have four raid 1+0 drives and I want to ensure they are correctly laid out so that if one controller channel fails it has the correct mixture of disks on the other channel to keep running. Thanks,
Poweredge T-420 with Perc 310 - how do controller ports relate to physical 
drives