I just got a new server that has a brand new Areca 1880 Raid controller which the built in arcmsr module does not support. Areca has updated module source code available on the cd that came with the controller and their website. Using this I was able to install Ubuntu Server on the hardware by using my laptop to build the kernel module and loading it off a USB stick.
I then built the driver for the server kernel and updated initrd but when I reboot it doesn't even look like Grub is getting loaded. The only thing the system does is display a "_" in the upper left of the screen. I believe I'm seeing a Grub issue but combined with the RAID controller/module issues I'm not 100% positive on that. Does anyone know of any limitations with Areca controllers and Grub?
One weird hurdle that I ran across is that the server install cd uses the desktop kernel rather than the server kernel so you need to build the module twice.
Looks like the only requirement is that the volume that Grub is installed on is less than 2TB. In my case it looks like Grub just didn't install properly and reinstalling grub sorted out my issues.
However I've now documented my procedure for installing Ubuntu Server on an unsupported raid controller. Hopefully this helps someone.