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Date: Thu, 31 Oct 1996 11:31:42 -0800
From: Julian Elischer <julian@whistle.com>
Organization: Whistle Communications
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To: FreeBSD SCSI list <freebsd-scsi@freebsd.org>
CC: Joe Karthauser <jlk@pavilion.co.uk>
Subject: Re: probing scsi bus after boot?
References: <199610311817.TAA16208@uriah.heep.sax.de>
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J Wunsch wrote:
> 
> (Moved to the freebsd-scsi list)
> 
> As Joe Karthauser wrote:
> 
> > Is it possible to reprobe the scsi bus after a reboot for allow for
> > drive swapping?  I guess that there must be some support for that in
> > there somewhere.
> 
> There's ``scsi -r'', though it used to be horribly broken for quite
> some time.  It worked fine in FreeBSD 1.1.5.1, and started to be ok
> again in -current of not too long ago (about a month or two).
> 
> _However_, drive _swapping_ is probably unsupported.  I think the sd
> driver gets royally screwed if you exchange the drive that was present
> at boot time by one with another total number of blocks later.  Even
> the `od' driver (that is supposed to catch up with such situations)
> doesn't do it right now, but there's a patch pending in one of the PRs
> that allows for it.
> 

you shouldn't need to reprobe to swap drives..
teh new drive will return
a "unit attention" error when first powered up
and that will invalidate all
information
on the drive.
the drive will then be inaccessible untill ALL references to it have
been closed
when that has happenned, ist should be possible to re-mount the new
drive.

(all in theory only mind you..
I haven't tried it, but it works that way for removable drives)

julian