I currently have two 1tb HDs in RAID 0 as my system drive and two 1tb drives in stand alone for storage. I wanted to know if I wanted to turn it into a RAID 0+1 array if I would lose the data on all 4 drives or just the two that I would be adding. Meaning would I lose my data on the system drive as well as the data on the two drives I am using for storage?
When creating a RAID 1, some systems will copy the data from the original drives onto the added drives, but you want to be certain that it will copy in the right direction. It would be unfortunate if it copied the new drives over the old.
I do not know what your particular motherboard will do. Even if it promises to do the right thing, however, I think it would be extremely foolish to count on it - a power failure at the wrong instant could really ruin your day.
You should get a large external drive (a 2TB would be good, but 1.5TB or 1TB might do if your system drive isn't full), and use something like Ghost to make a complete image of the existing system drive. Then add the drives.
If adding the drives works correctly, then you have a backup of your system as at the moment you did this - backups are GOOD!
If adding the drives messes up your data, then can restore the image to the created RAID array (so you lose nothing), and you still have a backup of your system as at the moment you did this - backups are GOOD!
Sounds like you win either way, doesn't it?
If you were feeling paranoid, you could always get a second external drive, and make TWO images of the system drive...
I have a 2tb external hd as well as several smaller (250gb or less) external hds that have all my data from the storage drives and everything else of importance backed up. As far as losing the data on my system drive I am not worried if it does end up getting lost it just inconveniences me as I have everything worth saving backed up already I am just curious as to what to expect. I was originally thinking of making a RAID 5 array but figured a 0+1 would be easier and less hassle.