[wellylug] RAID1 on OS disk

Jethro Carr jethro.carr at jethrocarr.com
Fri Oct 24 11:58:27 NZDT 2008

On Fri, 2008-10-24 at 10:57 +1300, E Chalaron wrote:
> Hi there
> Just a technical question before I bugger my PC...
> I need a Raid 1 for my operating system. Data are irrelevant the can be 
> reproduced easily and they already are on RAID 0 on 2 other disks.
> I was wondering when one uses a soft RAID 1 with Linux, how can a Linux 
> kernel  detect a faulty drive, if it already can't boot ? :-[
> Am I not better off using a BIOS RAID 1 to preserve operating system ?
> I can always do a dd I suppose, but it is a bit heavy.

I use software RAID on most my systems - the major advantage being that
it's much easier to monitor and control than hardware RAID.

Software RAID 1 will work fine with a faulty disk when booting, provided
that you have configured the boot loader correctly.

The important thing is to make sure the boot loader is installed to the
MBR of *both* drives, so that when the system boots, the BIOS will boot
from whatever drive it first finds which is working.

Once the bootloader starts the kernel, the kernel starts the RAID and
boots from the good disk.

I guess it would be possible for a disk to fail in such a way the
bootloader starts but the kernel fails to start, but I've never heard of
such an event occurring.

Jethro Carr
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