Maximizing RAID10 array SSD Speeds R730xd PERC H730 Mini 24 disks

Hi all,

I'm currently running an R730xd 12x 3.5" + 4x 3.5" Midplane chassis that's lined with 16x PM1643a's in a single RAID10 array on the PERC H730 Mini onboard controller.  I'm doing some minor upgrades including swapping to a 24 bay 2.5" chassis and I've been looking to eventually expand the RAID10 to 24x PM1643a's.  Based on the best research and info I could find for days, I believe I'm already hitting a sort of speed bottleneck, and the 24x disk array wont even be possible since the maximum I'm reading on this setup would be 16 disks in a single array (which I currently have).  So, I've been wondering what my options are.

The first question I have is related to the above pre-existing bottleneck I think I have.  Given the PM1643a is essentially maxing out the 12Gbps SAS interface at 1700MB/s, and since I have 16 of them, am I correct in assuming the 16 disks are sharing only 8 total SAS ports at this speed based on the H730 specs?  If so, would this mean that each SAS backplane slot is only getting 6Gbps instead of 12Gbps?  Having said that, if I filled out the array to 24 disks (if possible) it'd be docked even further to 3Gbps per SAS backplane slot?

The 2nd part is if the above slashes in speeds are indeed accurate, what are my options here?  The first thing that came to mind was adding a couple PERC cards to the PCIE slots... but this introduces other variables including if my 2x E5-2699's have enough PCI lanes for this and what this sort of setup would look like.  If I got an extra 2 PCIE PERC controllers and dedicated 8 disks per controller, is there a way to easily create a big 24x RAID10 array that's leveraging 3 total controllers?  Or would I have to do something like create 3x RAID10 arrays of 8 disks each, and then software RAID them after the fact?

If anyone could shed some light onto how to tackle this issue here it'd be greatly appreciated!  Thanks!