[CentOS] Re: RAID5 - MBR and default grub config on CentOS 4

Mon Aug 29 17:40:07 UTC 2005
Bryan J. Smith <b.j.smith at ieee.org>

 Robert Hanson <roberth at abbacomm.net> wrote:
> greetings, 
> i just know i have read several times on this list and in
> other places that on a RAID5 array that the MBR should be
> placed on the /boot partition.

Let's clarify that is a software RAID-5 (via MD).

And I don't think people mean the master boot record (MBR),
which can only go in cylinder 0 of the hard drive -- before
any disk slicing.

They mean you should make a separate /boot filesystem where
the kernel and initrd go.

> is this truly correct and if so, why?

Because kernel and any initrd (which contain the software
RAID support) must be loadable by the 16-bit Int13h Services.

If the /boot directory is in a filesystem that is a
software/OS stripe set (such as RAID-3/4/5/6/etc...), then
16-bit Int13h Services can't read it.

> my experiences of putting the MBR on the /boot partition
> are contrary to that it will even work and boot that way...

Correct.  I think they are referring to the kernel/initrd
files in a separate /boot filesystem that is not software
RAID (or only RAID-1/mirror).



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