Subject: Re: Another changer, another changer problem
To: NetBSD-current Discussion List <>
From: Curt Sampson <>
List: current-users
Date: 10/08/1998 12:45:26
On Wed, 7 Oct 1998, Greg A. Woods wrote:

> The scsibusN assignment must be done on the basis of whatever physical
> identification there is.  For hardware using slot assignment that means
> you have to configure the kernel as if there could be a scsi controller
> in every slot, thus if you use "pseudo-device scscibus N" then N must be
> equal to the maximum number of slots in the machine and the mapping of
> controller assignments to scsibusN must be done using the "slot" number.

Uh oh. This gets big pretty quickly, in the PCI situation. On a
PCI bus we may have up to thirty-two packages (a package being a
single on-board device, or a device on a card inserted into a slot),
each of which may have up to eight functions. So that's 256 potential
locations for SCSI controllers right there. However, we may also
have up to 256 PCI buses on a system, giving us 65536 potential
locations for a SCSI controller in our system. (This, of course,
assumes that we have only a PCI bus, and don't support any other

Now how exactly do we map all these potential controllers into your

And how do we deal with motherboard swaps. If I'm using this
`consistent' system, and I replace the motherboard with a different
model (which is likely to mess up my PCI slot ordering to a great
degree), do I have to go through /etc/fstab, my Oracle configs,
and everything else that wants to know about particular disks and
change it all? (Right now I deal with this by looking through the
boot messages to figure out that the controllers in the first three
slots that were on devices 7, 8 and 9 are now on 10, 12 and 11,
and build a new kernel to hardware these appropriately. I then need
change *nothing* else on my system; it's all done in one place.
This is very convenient for system administrators, as you can
imagine, and I wouldn't want this facility to disappear.)

Curt Sampson  <>  604-257-9400    De gustibus, aut bene aut nihil.
Any opinions expressed are mine and mine alone.
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