There’s bug out on 11.2 for RAID installation, and I’m not sure about Nvidia “Fake RAID” driver, those are liable to leave you with an undocumented & troublesome disk format, with a rarely deployed driver under Linux.
For this I would advise using Linux RAID tools. Just partition your disk more than you would normally.
On the other disk, duplicate partition sheme for anything you may want to mirror.
Once you’ve installed you can change data filesystems to md(4) mirror devices, with just one physical partition in mirror at first, then add partition from 2nd disk to install the mirroring.
By seperating out /boot, you can mirror that to simply, and have fall back GRUB entries in /boot/grub/menu.lst to boot from either disk.
Finally, Switch to mirroring ‘/’ and testing that. It’ll need changes to the initrd’s used, so the loaded kernel can load modules for mirrored device when it mounts the root filesystem.