> I'm installing a RAID1 with two 3TB drives, almost all of the volume is in the first partition, /, and about 35 GB is swap.  I tried to use cfdisk to partition the disks, but that did not work because they are larger than 2TB.  So I used parted, then gparted to make the partitions "raid" type, then mdadm, and it all looked good.  I did all that from the Ubuntu 12.04 live CD (but had to install mdadm).  I had to do that because the 2TB limit for fdisk is because of DOS label, and to get beyond that I had to use the GPT label.
>
> Next I went to the Ubuntu 12.04 Alternate CD (both CDs were AMD 64) and did the installation into the / partition, using ext4.  That went great up until near the last step when it tried to install GRUB in the Master Boot Record (MBR).  That step failed, returning this message:
>
> Unable to install GRUB in /dev/sda
> Executing 'grub-install /dev/sda' failed
> This is a fatal error.
>
> Everything was being installed to /dev/md0 (/) and /dev/md1 was swap.
>
> Apparently, GPT is an alternative to MBR, so that could have something to do with grub-install failing to install GRUB to the MBR.  (Ya think?). So I'm not even sure of why I tried, but I didn't know what else to do at 5 am yesterday morning after fighting with this thing all last night! Now I'm back at it.  I decided to continue the Ubuntu installation after the failed step.  I see this message:
>
> "No boot loader has been installed, either because you chose not to or because your specific architecture doesn't support a boot loader yet.
>
> "You will need to boot manually with the /vmlinuz kernel on partition /dev/md0 and root=/dev/md0 passed as a kernel argument."
>
> That to me is completely incomprehensible.  Do they mean that I should boot from a USB or CD?  Then do what, exactly?  Google gives so much that's just all over the map that I don't know what to do with it.
>
> If I run the Live CD, I can't see the /dev/md0 or /dev/md1 RAID1 partitions and if I run the Alternate CD, which handles RAID, it doesn't have the Live CD feature.

m-
sorry no experience with discs that big, but i'll offer my thoughts in
case it helps.  perhaps "grub-pc" ("grub2") just won't do it.  i'd try
"grub" next.  if you need further options, then try lilo, then
syslinux.  but how do you "try" them?  does that installer support
"legacy grub"?  probably not, or i would think you would have seen it
as an option.  it may be easiest to choose an installer (and the
distro that goes with it) that supports your hardware.  perhaps debian, perhaps
centos, perhaps fedora, perhaps opensuse.  or if you would rather
stick with ubuntu, it may be easier to skip using an installer
entirely, just prepare your raid, mkfs, unpack the core tar.gz, chroot
into it, apt-get install grub (legacy), see if it boots, and apt-get
install whatever else you want, eg whatever-desktop.  all easy if the
liveCD kernel supports your raid.  if not you may need to install to a
temporary small nonraid partition just to perform the rest of the
manual install (then later reuse the temporary partition as part of
raid swap or whatever).  see
help.ubuntu.com/12.04/installation-guide/amd64/linux-upgrade.html
-g