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Date:      Sat, 27 Jun 2009 08:42:55 -0600
From:      Scott Long <scottl@samsco.org>
To:        Kamigishi Rei <spambox@haruhiism.net>
Cc:        Alexander Motin <mav@freebsd.org>, FreeBSD-Current <freebsd-current@freebsd.org>
Subject:   Re: RFC: ATA to CAM integration patch
Message-ID:  <4A462FEF.3040601@samsco.org>
In-Reply-To: <4A462A7A.20005@haruhiism.net>
References:  <4A4517BE.9040504@FreeBSD.org> <20090627141412.GN31709@acme.spoerlein.net> <4A462A7A.20005@haruhiism.net>

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Kamigishi Rei wrote:
> Hello, hope you're having a nice day,
> 
> Ulrich Spörlein wrote:
>> I, personally, think this is not very good idea. People are used to
>> CAM-devices getting enumerated as da0, da1, etc. All the documentation
>> talks about ad0 for ATA and da0 (plus camcontrol) for SCSI, USB,
>> Firewire devices. We also have fd0 and cd0 and should stick to
>> two-letter-plus-number codes. So either make them all ad0 or da0. I'd
>> vote for the latter, as that is what Linux is doing (more or less) and
>> people are already familiar with USB drives or new SATA drives showing
>> up as "SCSI drives, so they get the SCSI names".
>>   
> This poses the question of daXX enumeration order. I've already had some 
> 'fun' with an IBM server which has an LVD/320 SCSI controller. While the 
> controller's bus was enumerated properly, somehow if you attach an USB 
> mass storage device before the system boot that said mass storage could 
> suddenly appear earlier than one of the SCSI disks (that was on 
> 7.0-RELEASE) thus breaking the boot process sometimes (when it appeared 
> as da0).
> 

CAM allows you to statically set the enumeration order via hints in
either the kernel config file or in /boot/loader.conf.  /sys/conf/NOTES
contains information and examples of this.

Scott



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