order of disk recognition

order of disk recognition

[Charu Chaubal]

I was wondering how to force the kernel to always assign the same device drive 
letter to the same physical disk.  I have two SCSI controllers.  Attached to one 
is the disk which contains my UltraPenguin distribution.  On the second one, I 
sometimes have disks attached, and sometimes not.  If I don't have disks 
attached, it labels the disks on the first controller as sda and sdb.  However, 
if I *do* have disks on the second controller, then those get labeled sda, sdb, 
sdc, and the disks on the first controller get labeled sdd and sde.  This causes 
problems because it is setup to mount partitions sdb1, sdb2, sdb3, etc.

short of having two versions of /etc/fstab, how could I have the first 
controller always be recognized first?  I believe it would involve adding 
something to the kernel boot parameters, eg. in silo.conf have a line 
"append=xxx=yyy", but I'm not exactly sure what to fill in for the xxx and yyy.  
Something to do with a driver name and base address?

Thanks (please ask if you need more details),
	Charu

Re: order of disk recognition

[David Miller]

   Date: 	Fri, 2 Apr 1999 08:53:21 -0800 (PST)
   From: Charu Chaubal <chaubal@ha3mpk.Eng.Sun.COM>

Short answer, there is nothing you can really do.
(Didn't I tell you this in private email?)

   Thanks (please ask if you need more details),

Longer answer, you may get something a little bit satisfatory on PCI
systems if you specify the "pci=onboardfirst", at least here the
device ordering will be slightly more sane but it's a hack and doesn't
provide a real solution.

Later,
David S. Miller
davem@redhat.com

Re: order of disk recognition

[Jakub Jelinek]

> 
>    Date: 	Fri, 2 Apr 1999 08:53:21 -0800 (PST)
>    From: Charu Chaubal <chaubal@ha3mpk.Eng.Sun.COM>
> 
> Short answer, there is nothing you can really do.
> (Didn't I tell you this in private email?)

Actually, there is something you can do. Start using devfs. Then the devices
won't change unless you reorder the SCSI controllers themselves (as opposed
to just detaching/attaching new SCSI devices to them).

Cheers,
    Jakub
___________________________________________________________________
Jakub Jelinek | jj@sunsite.mff.cuni.cz | http://sunsite.mff.cuni.cz
Administrator of SunSITE Czech Republic, MFF, Charles University
___________________________________________________________________
UltraLinux  |  http://ultra.linux.cz/  |  http://ultra.penguin.cz/
Linux version 2.2.5 on a sparc64 machine (3958.37 BogoMips)
___________________________________________________________________

Re: order of disk recognition

[David Miller]

   From: Jakub Jelinek <jj@sunsite.ms.mff.cuni.cz>
   Date: 	Fri, 2 Apr 1999 22:57:58 +0200 (CEST)

   Actually, there is something you can do. Start using devfs. Then
   the devices won't change unless you reorder the SCSI controllers
   themselves (as opposed to just detaching/attaching new SCSI devices
   to them).

I have a feeling Linus won't ever put this in for the 2.2.x stable
series and defer it to 2.3.x development kernels.

So what we will be able to offer users by default will not have this
functionality, they'll have to obtain it as a seperate kernel patch.

Later,
David S. Miller
davem@redhat.com