Re: PATCH: allow installing grub on the MBR if /boot is on mdraid.

[Jeremy Katz <katzj redhat com>]

On Wed, 2008-11-26 at 12:06 +0100, Hans de Goede wrote:
> This patch removes a special case when /boot (or / without a separate /boot) is 
> on mdraid. For some reason we only allow installing grub to the mdX device then 
> instead of allowing both the mbr of the 1st disk and the device holding /boot.
> 
> I've searched through the anaconda history and this special handling of mdraid 
> /boot has been there since before Feb. 2002, it was inherited from before booty 
> was introduced and it does not seem to make sense. Either we cannot have /boot 
> on mdraid at all (in all cases except for raid1) or we can have /boot on dmraid 
> (in case of raid1) and then it does not matter if the bootstrap of grub starts 
> on the mbr or on the first sector of a partition.

The reason we install to the mdX device is so that if your disk dies,
the bootloader install is mirrored[1] to both disks.  So while it is
technically possible to install to the mbr of the first disk, doing so
loses the redundancy of the RAID install.

Jeremy

[1] Although this functionality has wavered a bit between working and
not since we switched to grub long long ago.  It should be working these
days though afaik