There used to be a page here that described a somewhat convoluted scheme for tricking an old RedHat installer into doing a mirrored-root install. It is definitely doing it the hard way relative to more recent releases. As several folks have found it more confusing than helpful, I've tossed the page. Since you're installing a more recent release, you can make /, /boot, etc all mirror sets in the disk configuration utility initially, and the installer just does the right thing. And you can use either Grub or LILO, as both of them understand RAID mirrors for / and/or /boot. So you just make partitions on both drives that are type RAID, and then use the "Make RAID" button to join them into md0, md1, md2, etc. and label them as /, /boot, /usr etc. If you find any of these convoluted tricks people were doing to make the 7.1 or 7.3 installers do a bootable RAID config, it's really not neccesary any more. Marc