[CentOS] Software RAID muck up

[alex at milivojevic.org]

Quoting "Bryan J. Smith" <b.j.smith at ieee.org>:

> The problem with this is the fact that BIOS device addresses _change_
> when you remove a drive.  So do you setup GRUB on the 2nd+ device to be
> BIOS fixed disk 81h (the first device has failed, but has not been
> removed) or BIOS fixed disk 80h (the first device has failed and has
> been removed)?
>
> Even though the Linux device name might not change, GRUB needs to know
> what BIOS fixed disk assignment the disk is, and that _could_ change on
> the 2nd+ redundant boot devices.

Hmmm...  I think I read somewhere that if "root" directive is omitted, 
grub will
default to first partition of whatever disk it was booted from.  Or something
like that.  Basically, remove all root lines, and feed this to grub (each
install command should be one line, in case your mail reader breaks them):

install --stage2=/boot/grub/stage2 (hd0,0)/boot/grub/stage1 (hd0)
(hd0,0)/boot/grub/stage2 p (hd0,0)/boot/grub/grub.conf

install --stage2=/boot/grub/stage2 (hd1,0)/boot/grub/stage1 (hd1)
(hd1,0)/boot/grub/stage2 p (hd1,0)/boot/grub/grub.conf

quit

Also, if you keep your boot drives to be the first two drives in the 
system (or
if they are the only two drives), then configuring Grub to load its stuff from
first drive is usually a safe bet (as long as failed drive failed completely,
not visible by the BIOS).

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