[NMLUG] another boot issue

[michaelm at nnmcc.edu (michaelm@nnmcc.edu)]

Ed Brown said:
> Situation:
> two servers, with:
> motherboard with two onboard SCSI controllers
> one internal SCSI drive, with linux installed
>
> and:
> one external raid array, with just data, sometimes plugged into one
> server (via a scsi connector on the back panel), sometimes plugged into
> the other (The servers are brought down before before moving the raid
> array around.)
>
> problem:
> When the external array is plugged into the back panel connector, the
> BIOS finds it first, and Linux also wants to identify it as /dev/sda
> The mount points in /etc/fstab use 'LABELS', so they work however the
> internal drive is recognized.  But the system won't boot at all when the
> external array if first plugged in, unless you go into the regular BIOS
> and select the second drive for booting.

Do you mean that the BIOS is looking for a boot loader on a drive in the array?

> ('hard drive' is only listed
> once in the boot order selection; a separate menu item lets you choose
> the order of discovered drives - this is refreshed each time the machine
> boots, it isn't static)
>
> questions:
> What mobo manufacturer madness would allow the external scsi connector
> to have precedence in the discovery sequence?

Is it the BIOS or is it the assignment of the SCSI IDs?  SCSI will boot from
drives with ID 0 or 1, and if one of these is assigned to the external port,
could that be (part of) the problem?

> Why does linux make the same mistake?

Same reason?

> Any suggestions on how to overcome?

If nothing else, could you put a boot loader in the 'wrong' MBR that the
BIOS insists on using that simply chains to the 'real' boot loader?

> I think this is a hardware problem only, pre-grub, because after the
> POST and BIOS sequences, we just see a flashing cursor, no grub or
> kernel messages at all.
>
> thanks,
> Ed
>

-- 
Michael Maddex -- Instructor
Computers, Engineering and Technology
Northern New Mexico Community College

"The best way to predict the future is to invent it."
-- XEROX PARC