Paul, What do you think the chances are of a FC2 to FC4 upgrade working? Specifically I have a software RAID-1 using to SATA drives and am concerned about that surviving the upgrade process.
I've never done this so I can't say for certain. However, I would approach the upgrade with confidence because:
(a) mdadm identifies RAID volumes by scanning the partitions, not by looking for specific devices, so it should still work even if the device names have changed between FC2 and FC4.
(b) if it isn't going to work, you'll find out at an early stage of running anaconda because it won't be able to find the filesystems for your existing system when it's looking for a system to upgrade. So you could just reboot at that point and be back in FC2 where you started from.
Paul.
