Can I define SCSI device order?

[Paul Furness <paul.furness@vil.ite.mee.com>]

Good morning everyone.

I'm building a new system. It's a Dell Poweredge 2650 which has an
embedded SCSI controller with 2 HDD's attached. It also has in it an
Adaptec 39160 PCI card, which I want to use for external SCSI devices.


The plan is: Build the system (installing RedHat 7.3 + patches), and
then plug in the external RAID array which presents itself as a single
SCSI device.

The problem is that when I plug in the external array, it takes over as
"sda", shunting the disk with linux on it up to "sdb". This means that
it can't find the root partition, so although it starts booting from the
right place, it then kernel panics.

I _could_ change the configuration of grub and also fstab so that the
system boots happily from sdb, but then it is a problem if I remove the
disk array. Since there will be a backup system with exactly the same
hardware but no array, I need to be able to plug in the array and boot
the system without any messing around changing grub and fstab.

I investigated the PCI assignments of the SCSI controllers, and it shows
that the external one has PCI address 1:08.0 and 1:08.1, while the
internal one has 5:06.0 and 5:06.1. There are three PCI slots I can use
for the external card, and they come up as 0:xx.x, 1:xx.x and 2:xx.x, so
there is no way to get the internal SCSI controller to appear earlier on
the PCI bus than the external one.


So the question is: can I stop the external array taking over sda?  

Any ideas, anyone?

Paul.




-- 
Paul Furness

Systems Manager
Visual Information Lab
Mitsubsihi Electric ITE BV
Guildford, UK

Steepness is an illusion caused by flat things leaning over.