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Date: Thu, 9 May 1996 13:13:23 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199605090313.NAA04873@godzilla.zeta.org.au>
To: asami@cs.berkeley.edu, current@FreeBSD.org
Subject: Re: more than 32 scsi disks on a single machine ?
Cc: nisha@cs.berkeley.edu
Sender: owner-current@FreeBSD.org
X-Loop: FreeBSD.org
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>Can we connect more than 32 disks on a single machine?  I tried

No.

>Investigating further, I found this is in <sys/types.h>

>#define	makedev(x,y)	((dev_t)(((x) << 8) | (y)))	/* create dev_t */

>So it seems like we're limited to 32 disks.

This limits us to 16777216 disks, or only 8388606 disks if we avoid using
the high bit to avoid sign extension bugs.  The limit is in dkunit() in
<sys/disklabel.h>

>Will really bad things
>happen if I try to change this?

There are lots of things to change.  The encoding would have to be really
ugly to preserve compatibility with existing device nodes.

Will devfs handle this correctly?

devfs on't help.

Bruce