Grub Broken with onboard scsi + raid card

[Rick Stevens]

Todd Carter wrote:
> Redhat loads fine to a 3ware Raid 5 array and recognizes a scsi drive 
> attached to the onboard scsi interface.
> 
> After the install and reboot Grub reports a "Hard Drive Error" and quits.
> 
> However, if the scsi drive is disconnected from the motherboard then it 
> boots fine from the Raid Array.
> I would like to be able to use both of these drive interfaces.  Is there 
> any way to get them to co-exist?
> 
> I have no partitions on the scsi (sda) drive.  I load RedHat and Grub to 
> the MBR on sdb (Raid Card) and made sure I changed the drive order in 
> the install interface.  The bios hard drive boot order has the 'add-on 
> card' then 'scsi drive' in that order.
> 
> I've read that Grub can get confused as to what the bios is telling it 
> as far as drive information  but am not sure how to proceed
> from there. How do I find out what information the bios is giving Grub 
> in order to re-map the drive?  If that's what needs to be done then I'm 
> unsure about the procedure.

BIOSes often renumber devices regardless of the boot order.  The trick
is that, when the drive is connected to the on-board SCSI, your BIOS is
probably regarding it as device 0x80 (even though it's not the boot
device) and the RAID as device 0x81.

When the drive isn't connected, device 0x80 is the RAID.  When you
installed grub, it probably was with the internal SCSI disconnected, so
grub wrote the config file as having the root volume on device 0x80 (hd0
in grub parlance).  However, when the drive is connected, the RAID 
becomes 0x81 again (hd1 in grub parlance).

Boot with the drive disconnected.  When Linux comes up, edit
/boot/grub/grub.conf and change the references in it from "hd0" to
"hd1" (ALL references).  Then shut down, reconnect your SCSI drive and
power back up.  I'll bet it works.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-   Never test for an error condition you don't know how to handle.  -
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