Greg Helledy on 14 Nov 2014 13:57:42 -0800

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Re: [PLUG] Real (driverless) hardware RAID controller for PC?

To resurrect a topic from a few weeks back:

We got the new hardware, I have the BIOS set to AHCI for both of the
identical hard drives.  They are partitioned like this, following the
distribution's (ClearOS) RAID setup guide:

/dev/sda1	4000MB	swap
/dev/sda2	 500MB	/boot	/md0
/dev/sda3	(rest)	/	/md1

/dev/sdb1	4000MB	swap
/dev/sdb2	 500MB	/boot	/md0
/dev/sdb3	(rest)	/	/md1

The install asks you where you want to put GRUB, with the default being
the MBR of /dev/sda.

Later in the instructions, they link to a separate page on installing
GRUB on the secondary drive.  The command given is "grub-install /dev/sdb".

The command succeeds, but in my case it rendered the system unbootable. I don't understand why this would be. /boot/grub/ has:

(hd0)	/dev/sda
(hd1)	/dev/sdb

I found this howto on bootable RAID1 for CentOS:

Unlike the documentation for ClearOS, the CentOS writeup is emphatic
that a RAID1 /boot partition is risky, silly and only for hobbyists.

However, they outline a method for installing GRUB to both HDs.  I
followed it, without fully understanding what I was doing.  It worked
(the system is bootable), but I am concerned about the warning that I will:

end up with a fragile result that is not updated when a software
update installs a new kernel. We do NOT recommend it. Years of
experience demonstrate that is is highly likely that you WILL forget
to do a bootloader refresh, and run a greater risk of losing data,
than the theoretical risk of a hard drive failure.

The steps I took were:

grub> device (hd0) /dev/sda
grub> device (hd1) /dev/sdb
grub> root (hd0,1)
grub> setup (hd0)
grub> root (hd1,1)
grub> setup (hd1)
grub> quit

Apparently an update of either the kernel or glibc will now render the system unbootable? Did I make a mistake doing this?

If I had to guess, the "grub-install /dev/sdb" command somehow pointed the root to partition 0 (swap) instead of 1 (boot).

Greg Helledy
GRA, Incorporated
P:  +1 215-884-7500
F:  +1 215-884-1385

On 10/23/2014 2:41 PM, Greg Helledy wrote:
Thanks again, everyone!  I will certainly do the suggested reading
on this topic.  Since the OS passed the test we'll be upgrading to
new hardware soon and I wanted to be sure I understood the true

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