Question on MBR of SATA Raid 1 Software

[Bruno Wolff III]

On Fri, Mar 02, 2007 at 14:30:51 +0100,
  Dario Lesca <d.lesca at solinos.it> wrote:
> I have install my fc6 server with RAID-1 software on 2 SATA HD.
> All work fine.
> 
> My question is:
> 
> If HD1 crash, HD2 is ready for boot the system? I have see witch the MBR
> of the 2 disk is different. (see follow explanation)...
> 
> I must copy with this command:
> 
>   # dd bs=512 count=1 if=/dev/sda of=/dev/sdb
> 
> MBR of first disk on MBR of second disk?
> 
> Or this operation is not necessary?

Currently grub is not software raid aware and the default is to only install
it on one of the mirrors. You want to manually install it on the other
drive as well, but when you do it should be set up to install from hd0, not
hd1 (even though it is being put on hd1) because most likely after a drive
failure hd1 will been seen as hd0. Unfortunately grub doesn't seem to
have a way to say install off the current drive no matter what drive number
it is.
grub2 is going to have some ability to use software raid, but the last time
I checked it, it didn't work.