It’s just a heads up how to configure a P7 hardware, if you want to have a triple split backplane.
If you add an additional SAS controller (FC 5901) together with few special cables, you can split the internal disks in the system unit enclosure.
Remember to connect the cable FC 3679 to the top port of the SAS controller.
Otherwise, you need to restart the machine if the cable is wrongly connected.
More information here