Fedora Installation :: F12 Won't Boot On LVM/RAID System After Upgrade

I upgraded from F10 to F12 using preupgrade. The upgrade itself completed with no errors, but I'm unable to boot afterward.

Symptoms:...Grub starts, the initramfs loads, and the system begins to boot. After a few seconds I get error messages for buffer i/o errors on blocks 0-3 on certain dm devices (usually dm0 and dm2, but I can't get a shell to figure out what those are). An error appears from device-mapper that it couldn't read an LVM snapshot's metadata. I get the message to press "I" for interactive startup. UDEV loads and the system tries to mount all filesystems. Errors appear stating that it couldn't mount various LVM partitions. Startup fails due to the mount failure, the system reboots, and the steps repeat.

Troubleshooting done:...I have tried to run preupgrade again (the entry is still in my grub.conf file). The upgrade environment boots, but it fails to find the LVM devices and gives me a question to name my machine just like for a fresh install. I also tried booting from the full install DVD, but I get the same effect. Suspecting that the XFS drivers weren't being included, I have run dracut to create a new initramfs, making sure the XFS module was included. I have loaded the preupgrade environment and stopped at the initial GUI splash screen to get to a shell prompt. From there I can successfully assemble the raid arrays, activate the volume group, and mount all volumes -- all my data is still intact (yay!). I've run lvdisplay to check the LVM volumes, and most (all?) appear to have different UUIDs than what was in /etc/fstab before the upgrade -- not sure if preupgrade or a new LVM package somehow changed the UUIDs. I have modified my root partition's /etc/fstab to try calling the LVM volumes by name instead of UUID, but the problem persists (I also make sure to update the initramfs as well). From the device-mapper and I/O errors above, I suspect that either RAID or LVM aren't starting up properly, especially since prior OS upgrades had problems recognizing RAID/LVM combinations (it happened so regularly that I wrote a script so I could do a mkinitrd with the proper options running under SystemRescueCD with each upgrade).

I have tried booting with combinations of the rootfstype, rdinfo, rdshell, and rdinitdebug parameters, but the error happens so early in the startup process that the messages quickly scroll by and I just end up rebooting.

System details:4 1-TB drives set up in two RAID 1 pairs. FAT32 /boot partition RAIDed on the first drive pair. Two LVM partitions -- one RAIDed on the second drive pair and one on the remainder of the first drive pair. Root and other filesystems are in LVM; most (including /) are formatted in XFS.

I've made some progress in diagnosing the issue. The failure is happening because the third RAID array (md2) isn't being assembled at startup. That array contains the second physical volume in the LVM volume group, so if it doesn't start then several mount points can't be found.

The RAID array is listed in my /etc/mdadm.conf file and identified by its UUID but the Fedora 12 installer won't detect it by default. Booting the DVD in rescue mode does allow the filesystems to be detected and mounted, but the RAID device is set to be /dev/md127 instead of /dev/md2.

The arrays are on an MSI P35 motherboard (Intel ICH9R SATA chipset) but I'm using LInux software RAID. The motherboard is configured for AHCI only. This all worked correctly in Fedora 10.