RAID & HDD failure recovery

[Bruno Wolff III]

On Fri, Nov 17, 2006 at 17:19:57 -0700,
  "David G. Miller" <dave at davenjudy.org> wrote:
> 
> BTW, to anyone reaching for their flamethrower, I don't want to start a 
> grub vs. lilo flame war so please don't.  If you have a *foolproof* and 
> *native* (doesn't rely on external commands) way to get grub to support 
> Linux software RAID, I'm more than willing to listen.  Hint, anything 
> that includes an instruction like "use dd to copy the MBR..." is a 
> non-starter.

The latest version (1.95) of grub 2 claims to support software raid.
However, it looks like it isn't really stable and there isn't documentation.

For the grub that comes with FC, it does work with RAID 1. You have to make
sure to install it on both drives. I am not completely sure, but in some
tests I did you can have stage 1 on both drives, but not stage 1.5.
What I do is:
root (hd1,0)  Assuming /boot is on the first partition.
setup (hd1)   This combination is what I think sets up stage 1.5 on hd1.
root (hd0,0)  This combination is so that if the current hd0 fails (so that
setup (hd1)   hd1 becomes hd0) it will use stage 1.5 from the correct drive.
setup (hd0)   Do the same for the normal boot drive.

At worst you will need to swap disks to be able to boot after a disk failure.
(So if you want to replace hd0 with a new drive, you need to put the current
hd1 on the cable currently used for hd0 and put the new drive on the cable
currently used by hd1.)