Oh wow.. I will need to study Sabayon some more before installing.. Turns out this board does have BIOS raid but its not true Hardware raid as it is loaded through firmware.. So that is why on boot Sabayon sees SDA & SDB under /DEV.. The device mapper doesn't see the raid volume till its mapped by the Installer...
This could pose a problem for grub later because of this http://en.gentoo-wiki.com/wiki/RAID/NVRAID_with_dmraid#Building_the_Kernel
Do not run grub-install! It will not work properly, and will probably detect the sda1, etc. instead of your actual raid. Make also sure not to start grub inside of an chroot enviroment like you propably do if you install from the Gentoo LiveCD and do it like described in the installation manual of gentoo.org. It doesn't know about /dev/mapper so you would get some errors with grub. In this case just jump into another terminal with ALT+F2. Start grub and make sure that it's pointing to /dev/null as a device map.
I am not sure if Sabayon installer will properly execute grub on the right device ie: /DEV/SDA1 where it should be /DEV/MD127
I'm going to simulate this In a VM and see if this boots software raid before installing, as that's how Sabayon is treating my system now; and to see if the installer is going to attempt to install grub on SDA1 or MD127..
Had I know before hand what I had, I would of probably avoided a RAID setup. Learn something new everyday I suppose, I'm not afraid of something new, just wish I was better prepared for this.
I just hope Sabayon is loading raid via Kernal instead of modules as this could make this easier.http://en.gentoo-wiki.com/wiki/RAID/Onboard#Configure_kernel
I am only using Gentoo information as a primer for Sabayon install.. I know things are not done the same 100% between Sabayon and Gentoo.. but because Sabayon may inherited some of the hiccups of gentoo I would rather be prepared for this situation. Not sure how much has changed with Grub2 so this may be outdated..