This is a known "issue" and is explained as follows:
Cannot boot with /boot partition on a software RAID array
link to this item - Bugzilla: #750794
Attempting to boot after installing Fedora 16 with the /boot partition on a software RAID array will fail, as the software RAID modules for the grub2 bootloader are not installed. Having the /boot partition on a RAID array has never been a recommended configuration for Fedora, but up until Fedora 16 it has usually worked.
To work around this issue, do not put the /boot partition on the RAID array. Create a simple BIOS boot partition and a /boot partition on one of the disks, and place the other system partitions on the RAID array. Alternatively, you can install the appropriate grub2 modules manually from anaconda's console before rebooting from the installer, or from rescue mode. Edit the file /mnt/sysimage/boot/grub2/grub.cfg and add the lines:
Now run these commands:
Adjust the device names as appropriate to the disks used in your system.
I had a system where I'd created a mirror for /boot that had been reinstalled from Fedora 13, 14, 15 and now 16. As reported, it failed to boot following the F16 install.
Destroying the mirror and creating a simple /dev/sda2 partition for /boot got it booting.