I just added a Dell Xyratex shelf with 12 LFF bays. 3.5" drives appear to be cheaper. I did crystal speed disk test on the response of the two systems and it is just about the same (unless you consider 250ms+/- a big boost in time). It was fun putting this heavy additional heating fan in my rack, as I will probably save more cost in heating my home this winter if I just pump air for the house out of this room. Yes that was a good solution.
I bought Xyratex AFTER I got my 2.5" cage. So now I solved my storage problem, I wanted to just finish the project to free up 2.5" bays so I have that ready when I need to use in probably 3 more months.
The HP DL3800 has one PCIe riser with (2) SAS cards, 1 for the existing 2.5" internal bank and 1 for the external 3.5" Xyratex bank. After shopping, I discover another PCIe riser will cost me a whole $10 and another LSI 9211 internal card is like $20 - the obvious solution here is to go with that.
Another option for me, I can also test my skills and attempt to convert the onboard HP R410 SAS controller to IT mode. There is some write-ups people have done it. Ideally that would be better, since I would not have another riser and PCIe card heating up the hardware crammed in that box.
