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Date: Sun, 1 Aug 2004 08:49:58 -0600 (MDT)
From: Scott Long <scottl@freebsd.org>
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To: Pete French <petefrench@ticketswitch.com>
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cc: freebsd-stable@freebsd.org
Subject: Re: How does CAM determine the order to number drives ?
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On Sun, 1 Aug 2004, Pete French wrote:
> > You can wire down particular devices to a given SCSI bus, target and
> > LUN.  Thus in your (4.x) kernel config you can say:
> >
> >     device scbus0 at ahc0
> >     device da0 at scbus0 target 0 unit 0
>
> Thanks for this - it looked as though it was just what I needed. I built
> a kernel with scbus0 placed at ahc? (ahc0 would not compile - but I only
> have one Adaptec controller in the machine). I would have thought this
> was sufficient as it would then scan scbus0 first and thus find the
> Addapted conntected drive first. But it did not appear to do this - I
> still had the ciss drives appearing first.

You need to explicitely define 'ahc0' as so:

device	ahc
device	ahc0	/* declared for wiring */
device	scbus
device	scbus0 at ahc0

Wiring down the controller number doesn't usually affect drive ordering.
All drives on all controllers are scanned at once in parallel, and the
first to respond on any controller, regardless of the controller number,
get to be da0.

Scott