You really do not want to do it this way. Setting up raid on a
partitions just seems like such a bad idea on so many levels. You
should do it on the entire disk. Last time I remember messing with it,
the setup screen for that was not capable of doing that.
How do you propose to do "entire disk"? Will you be using LVM on the system?
I have had very good success with the method I described, including several incidents of
failed drives. Clearly it's not as good as hardware RAID, but still I think
it is MUCH better than nothing. It is certainly the best mirroring solution
I have come across short of a hardware RAID controller.
Tom