From owner-freebsd-scsi  Mon Feb  7 13:26: 7 2000
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Date: Mon, 7 Feb 2000 22:55:33 +0100 (MET)
From: Gerard Roudier <groudier@club-internet.fr>
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To: Wilko Bulte <wilko@yedi.iaf.nl>
Cc: George Morgan <gemorga2@vt.edu>, freebsd-scsi@FreeBSD.ORG
Subject: Re: Rescan for Devices...
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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=20
> > devices on a scsi controller?  I'm actually trying to do this on an=20
> > OpenBSD 2.6 (sparc) machine, but I know there are some people=20
> > that really know SCSI well on this list...
>=20
> man camcontrol
>=20
> and then:
>=20
> camcontrol rescan <bus#>
>=20
> 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.=20

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.=20

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.=20

G=E9rard.



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