hehehe a month ago my old optical drive died and I purchased old (2007) but unused&unpacked TEAC IDE DVD burner for my PC. I could not go for SATA because my MB has only 2 SATA connectors.

I would:

RAID1 across the 128GB, 128GB of the 256GB and 128GB of the terabyte drives (/).
RAID1 across rest of the terabyte drives (/home)
Rest of 256GB for /tmp

That's some serious redundancy.

Does it protect at all against viruses or as I suspect it's just drive failures that it protects against because running RAID 1 means a virus on one drive equals a virus on all four??

Oh, also, how would I do this??

Create 1-128GB partition on the 128drive and call it C
Create 1-128GB partition on the 256drive and call it D
Call the rest of the 256 drive E
Create 1-128GB partition on the spinning drives and call them F (first 128 of the first drive), G (rest of first drive), H (first 128 of second drive), I (rest of second drive).

Then RAID 1 drives C, D, F and H and also RAID 1 drives G and I ???????

Is that right?

I really, really don't like my computer being down :P

Well.. using Linux does help against viruses :) but RAID does nothing.