[CentOS] Re: Add RAID after install in one disk

Wed Feb 28 17:27:27 UTC 2007
James Olin Oden <james.oden at gmail.com>

On 2/28/07, Scott Silva <ssilva at sgvwater.com> wrote:
> CM spake the following on 2/28/2007 5:40 AM:
> >> IIRC, you also have to do some special magic with the grub config to
> >> make the machine boot nicely even if you have to reboot with one drive
> >>
> >> down. Unfortunately, it's been a while since last time I did this, so
> >> I  can't remember.
> >>
> >> --
> >>   Haakon Gjersvik Eriksen     --                  Basefarm AS
> >
> > Presuming sda first HDD, sdb second HDD, first partition (0)  is /boot
> >
> > grub
> > device (hd1) /dev/sdb
> > root (hd1,0)
> > setup (hd1)
> >
> > CM
> >
> I'm confused. Wouldn't you want "root (hd0,0)"
> because if the first drive fails, the second drive will become sda after boot.
>
As I understand it the first drive does not become sda/hda after boot
in all cases.  At least with IDE drives it will always stay where it
is based on controller and master/slave relationship.   Beyond this,
though, when specifying "root" for the setup command grub taking the
drive in the context of how the BIOS has mapped who is the 0th, 1st,
2nd and so on, with a simple transform provided by your
/boot/grub/device.map file.  At least this is what I believe to be the truth.

...james