[X4U] MacPro RAID setup

[alexandre]

Hi

Last week I bought a MacPro 2x2.4GHz (mid 2010), with a 2TB hard drive. At the same time, I bought a 120GB SSD onto which I loaded OS 10.7.3 and all my applications. Over the weekend I'll be buying 4 3TB drives that I'll setup as a RAID. Since I'm not very familiar with RAIDs and despite some intense googling, I have a few questions. 

I understand the difference between RAID 1+0 and 0+1, but which is safer? I've read that one is better than the other but I haven't really understood why.

What are the advantages of a nested RAID over, say, 2 independant striped RAIDs where one is a Time Machine backup of the other?

I'm not so much interested in speed as I am in keeping my data safe. Should I go the nested RAID route (0+1 or 1+0), I will be backing up to 1 or 2 external FW 800 drives.

FWIW, I work a lot with photographs (RAW files).

Any tips or additional information is appreciated!

Regards, Alexandre