Did some more reading, and now I understand the difference between the motherboard offered RAID and Windows 7 RAID. I am going with the board RAID.
So I setup the RAID 0 of the two SSDs during the boot, using the "Intel RST Raid BIOS" utility. Now in Windows, using the "Disk Manager" utility, I can see a single drive listed, that is really the two SSDs in RAID. So I think that is ok. The drive was showing as "uninitialized", so I initialized it. Now it shows as "unallocated". If I right click on the drive, I have the option of setting up a "simple span", "striped span", etc. I think because I am using the motherboard RAID, and Windows effectively sees these two SSDs now as one drive, I should select the "simple span" option.
But next I can select the "allocation unit size". There is option for "default", or I can select from 512 up to 64k. Any advice on what to select?
(By the way, during the BIOS RAID setup, I was asked similar question, and I selected 64k. It was something to do with block size. Hope that was ok. I don't know if the two are related.)
Well I got the arrays setup and working - no issues. Using the motherboard BIOS RAID utility, I set the project/media array (2x 256gb SSDs) as having block size 128k. The scratch/preview array (2x 128gb SSDs) as having block size 64k. Then in Windows 7 Disk Manager utility, I initialized and then allocated the drives. I used the "simple span" option for each, because Windows considers each array as a drive at that point. Left the "allocation unit size" set to "default" for both drives.
Still need to execute some performance tweaking and benchmarking. But Windows at least indicated I was getting +700mb/s copying media files from one SSD array to the other (compared to around 120 mb/s copying from a single platter drive.) The SSDs are all Samsung 830 models purchased when the prices tanked a while back. They are connected to sata 6g ports on the board.
My workflow with these drives is as follows:
1) Copy new footage from source cameras to a 1TB platter array (RAID 1).
2) Start a new project on the 512gb SSD array (RAID 0), and copy footage to the project folder as needed from the platter.
3) Work on the project, using the 256gb SSD array (RAID 0) for scratch/previews.
4) Export to the platter.
5) Complete the project and move the entire project folder to the platter.
6) Backup the platter to an external drive occasionally, and delete projects that won't be needed again.
7) While working on important projects, occasionally backup to the platter as desired.
In the past, I tried using a single media footage source location and importing from there into all my projects. That had the advantage of no duplicated footage. But now I prefer each project with a footage folder as a self-contained unit, I find this easier for organizing, moving things and archiving. I tend not to work on many large projects at the same time, so hopefully the 512gb project/media SSD array and 256gb scratch/preview SSD array will suffice in terms of space. Will see how it goes - I plan to upgrade the 1TB platters to a larger size as some point but they are fine for now.