When using a Promise ATA Raid controller, you may need to reboot the box *AFTER* creating the partition before you can format it. Should be a notation of something like this on the user docs.
I'll take this
Please see http://dev.gentoo.org/~swift/gentoo-x86-install.html. I've added a new chapter/section on the bottom of the installation guide which tells the Hardware RAID users what to do when installing Gentoo Linux on their hardware. All references to RAID in the guide itself are removed to make it less cluttered. This will be committed to CVS if there are no objections from the review team.
Committed.