Cable with part number 8717G can be used to connect HBA 330 to front backplane.  I am not sure on whether on 12X3.5 config you can connect rear Backplane to another PERC controller.   
I have a Dell PowerEdge R730XD . It currently has a PERC H730 mini monolithic raid controller that connects to the front backplane, PWA JXTHC, ASSY FWXJR (12x3.5") via a short BP SAS B0/A0 cable with a PERC connector on one end, and a double-connection single-headed mini SAS right angle connector on the other end (presumably the cable is P/N 8717G). The rear backplane, PWA 7HWKR, ASSY 6WNVX (2x2.5") connects its mini SAS connector directly to the front backplane's SAS expander via a BP SAS A2 with a right angle connector on one end and a straight connector on the other end (presumably the cable is P/N 8RJM1). I am planning on replacing the PERC H730 mini monolithic raid controller with an HBA330 controller, as I do not want to use raid with the front 12 drives.  I plan on using ESXi's pass through feature on the controller to present the 12 disks to a VM for exclusive use.  Question 1: Is the cable I have (I assume it's the 8717G) proper to connect the HBA330 to the front backplane, or do I have to purchase a new cable with a different part number? I do not want to pass through the rear backplane flex bay drives, so I don't believe I can connect it to the front backplane anymore. I plan on purchasing a PCIe RAID card (H330 or H730, as the manual claims they are supported) for me to create a mirror of the two drives in the flex bay, so that I can boot ESXi from it.  Question 2: What cable would I need to connect the new RAID controller to the rear backplane using the mini SAS connectors? The goal is to have the front backplane on the HBA330 controller, so I can passthrough the drives connected to it, but to have the rear backplane connected to a separate controller so I can boot to a RAID mirror. Question 3: If any of the above poses a problem with my desired goal, what suggestions could be made to resolve it? A new front backplane? Having drives externally on an external RAID card like the H830? PCIe NVMe drives? etc. Thank you.
Dell PowerEdge R730XD Connect Rear Backplane 2x2.5" to PCI RAID instead of 
Front Backplane