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

[Jeremy Katz <katzj redhat com>]

On Tue, 2008-12-02 at 11:26 +0100, Hans de Goede wrote:
> Jeremy Katz wrote:
> > On Mon, 2008-12-01 at 18:58 +0100, Hans de Goede wrote:
> >> You are right studying the code further this does indeed happen. And installing 
> >> to the first sector of the raid set partitions should be fine, assuming that 
> >> the disk has a dos like mbr which just bootstraps to the bootsector of the 
> >> active partition, but what if the disk does not have a valid mbr?
> > 
> > This has come up from time to time.  One answer is that if we don't
> > detect something that looks like an MBR and we're doing this (or any
> > install /boot partition type installs), we should overwrite with a
> > "real" MBR.  The problem is that this could trample over some other boot
> > loaders which has been something we haven't been willing to do in the
> > past.  Maybe we should pop up a warning and default to doing so, but
> > give a way out if the user knows that they have a valid reason.  Even
> > though I hate those sorts of things :/
>
> I vote for just defaulting to installing on the MBR even in the raid1 case, if 
> the user wants the redundancy one gets from installing into the mdraid 
> partition, they can still easily select that. The user needs to have either a 
> special BIOS, or needs to modify the BIOS settings and / or remove the disk 
> when it died, which all require a very experienced user. I don't think it is to 
> much to ask this special group of users to change the selection from install to 
> mbr to install to partition during install if they want the additional 
> redundancy this gives.

That is a major change from what the behavior has been essentially
forever.  And it's the sort of change that leads to downtime and admin
cursing.  I really don't think that just installing to one MBR by
default if you're doing a RAID'd /boot is the intent or the desire... if
we're going to default to doing the MBR, then we need to do similar bits
to ensure that there's a boot record installed on both MBRs.

Jeremy