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Date:      Mon, 7 Feb 2000 14:38:33 -0700
From:      "Kenneth D. Merry" <ken@kdm.org>
To:        Gerard Roudier <groudier@club-internet.fr>
Cc:        Wilko Bulte <wilko@yedi.iaf.nl>, George Morgan <gemorga2@vt.edu>, freebsd-scsi@FreeBSD.ORG
Subject:   Re: Rescan for Devices...
Message-ID:  <20000207143833.A24212@panzer.kdm.org>
In-Reply-To: <Pine.LNX.3.95.1000207221417.341A-100000@localhost>; from groudier@club-internet.fr on Mon, Feb 07, 2000 at 10:55:33PM %2B0100
References:  <20000207191037.A386@yedi.iaf.nl> <Pine.LNX.3.95.1000207221417.341A-100000@localhost>

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On Mon, Feb 07, 2000 at 22:55:33 +0100, Gerard Roudier wrote:
> On Mon, 7 Feb 2000, Wilko Bulte wrote:
> > On Mon, Feb 07, 2000 at 10:12:57AM -0500, George Morgan wrote:
> > > Is there a way to use the *BSD command "scsi" to rescan for 
> > > devices on a scsi controller?  I'm actually trying to do this on an 
> > > OpenBSD 2.6 (sparc) machine, but I know there are some people 
> > > that really know SCSI well on this list...
> > 
> > man camcontrol
> > 
> > and then:
> > 
> > camcontrol rescan <bus#>
> > 
> > Works just fine.
> 
> Not really for me, may-be since I donnot want to rescan the bus, but to
> just scan the bus for devices that haven't been seen by CAM at boot for
> some reason. 
> 
> First attempt after having switched the box on and booted for the first
> time:
> 
> <Quantum XP32150W L912>            at scbus1 target 0 lun 0 (da3,pass4)
> <QUANTUM XP32275W LXY4>            at scbus1 target 1 lun 0 (da2,pass3)
> <IBM DDRS-34560W S71D>             at scbus1 target 4 lun 0 (da5,pass6)
> <QUANTUM XP32275W LXY4>            at scbus1 target 5 lun 0 (da4,pass5)
> 
> Second attempt after having rebooted the machine:
> 
> <Quantum XP32150W L912>            at scbus1 target 0 lun 0 (da4,pass5)
> <QUANTUM XP32275W LXY4>            at scbus1 target 1 lun 0 (da3,pass4)
> <IBM DDRS-34560W S71D>             at scbus1 target 4 lun 0 (da2,pass3)
> <QUANTUM XP32275W LXY4>            at scbus1 target 5 lun 0 (da5,pass6)
> 
> Problem is that the order of da# devices after first boot + scanbus 1 is
> different from order after second boot + scanbus 1. 

Which devices appear during the boot, and which ones appear after the
rescan?  It seems rather odd to me that your disks aren't showing up at
boot.  Are they not powered on or something?

> I guess the reasons given that xpt_scan_bus() is scanning targets
> (excepted the initiator obviously) in parallel. I would think that such a
> concurrent target scanning can be faster than a sequential scanning, only
> if some devices, that are too long for responding to SCSI commands used
> for the probe, (probably INQUIRY) disconnect the BUS during the scan. But
> if this happens, or if some devices are reporting transient problems, then
> order of devices cannot be guaranteed on successive (reboots) + (re)scan
> of BUS.
> 
> In my opinion, an option that will allow to request a sequential BUS
> (re)scan would be useful, not only for me. 

Devices are attached sequentially, unless you hard-wire them.  If you
rescan the bus, though, the disks are given the first available device
number.

If you want things to turn up in the same place every time, I would suggest
hardwiring your disk device numbers to a specific bus/target/lun.

Ken
-- 
Kenneth Merry
ken@kdm.org


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