Disk setup again

Question

Hi everyone,
I'm asking about a suggestion for HDD setup for using Adobe Premiere Pro 5.5. I did look at some general guidelines on the adobe forums, but my question is not 100% answered in there.
My specs right now are
i7-3820
Asus P9X79 Pro
eVGA Nvidia GTX 570 HD SC
16 GB (4x4) G.Skill Ripjaws Z 1600
PC Power & Cooling Silencer 760 W
Antec 902v3
x1 Crucial M4 SSD 128 GB, where I only put the OS and all my programs.
x1 Hitachi 7200 RPM 2 TB SATA III HDD.
Even though Adobe is installed on the SSD, it does all the work in the HDD (projects, exports, media, etc.). Apparently it's much better if I add another HDD to the system, which I am planning to do so. My very first option is to get an identical HDD drive as the Hitachi I already have. It just makes sense and it's a very good drive in my opinion.
Questions:
1) Would you advice to put these two HDDs in a RAID 0 array? (the guidelines mentioned above don't say so.. they only put RAID 0 starting from 3 work disks and not 2 as in my case).
2) Either way, could there possibly be any difference if I plug these HDDs onto SATA II ports? Cache of the HDD is 64 mb if that's relevant. The thing is that my MB has 4 SATA III ports, 2 of them are Intel and 2 of them are Marvell (mobo is Asus P9X79 pro). One of the Intel ports has the SSD. So if I want the HDDs to be on SATA III ports I guess the best would be to put them in the Marvell ports (either in RAID 0 or not). But I heard these ports are not very reliable for some reason and have some issues, is this correct? If they do have issues then I'll just put them in SATA II. (maybe one in SATA II and the other in SATA III if they are not in RAID?)
3) Do you really really recommend that I buy this second HDD? Or just one will be okay? For the moment we're working on small projects so the difference shouldn't be too noticeable, but on the long run I think it could be important, and I'd better buy it now to make sure I get the same drive in case I RAID 0-them. I'm kind of answering myself here, but any opinions are also welcome   We are editing almost every day of the week if that matters.
Thanks!
PS: I posted the same question on tomshardware forums, so I apologize if you read it twice

Answer 1

A volume (whether that consists of a single disk or multiple disks in a raid configuration) is seen by Windows as a single volume and that single volume still is hampered by the half-duplex nature of the SATA connection. In your case, one SSD and one (raid0) or two volumes (single disks) will still have to adhere to the SATA half-duplex nature, but as single disks it allows reading from one volume and writing to the other volume at the same time. That is faster than waiting for the reading to finish (even though the reading is faster on a raided volume) and then starting writing on the same volume. I would suggest not using a raid with only two disks. Reading this answer, I realize this is not well explained, I find it hard to make an analogy, but consider it like a single street where traffic is allowed to flow in one direction only at a certain time. It does not really matter if that traffic can drive at 30 or 50 MPH on that single lane, because the lane is too short to notice that speed difference. Then the traffic direction is changed and the flow from the other side can start to move. That is the half duplex nature of SATA, but what happens when you have two lanes available for traffic (two volumes in Windows speak), each lane may be slower to move but the overall movement of cars is still faster than over a single lane.