have 4 port module on MSA 500. Do I use 2x SA642 or 1x SA642 and 1x SA6402

[Stuart Robson]

I am consolidating some kit to make a high availability cluster.

I have:
2 x DL385 dual CPU, dual core servers with 2 x 36GB drives in each
1 x MSA500 with the high availability option inc 12 x 300GB drives and 4 port module.
4 x SA642 with no extra cache
2 x SA6402 with 512MB of cache

What is the best performance option I have available with this kit? Can you mix SCSI controllers on the same node?

Help greatly appreciated...