Installing Amahi with RAID 1 in 2HDD setup. See this other page for [[RAID5]].
In a Fedora forum thread - http://www.fedoraforum.org/forum/showthread.php?t=255048 it was found that some makes of hard drives can cause this problem as they take a while to spin up so the system ignores one of them and carries on with the degraded array.
To fix this, apply the recommended lines to your /etc/rc.d/rc.local file. Make sure you backup the file before doing this just in case and do this all as root.