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Date: Mon, 15 Oct 2007 09:35:50 -0400
From: Theodore Tso <tytso@mit.edu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Rob Landley <rob@landley.net>,
       James Bottomley <James.Bottomley@steeleye.com>,
       Matthew Wilcox <matthew@wil.cx>, linux-kernel@vger.kernel.org,
       linux-scsi@vger.kernel.org, Jens Axboe <axboe@suse.de>,
       Suparna Bhattacharya <suparna@in.ibm.com>,
       Nick Piggin <piggin@cyberone.com.au>
Subject: Re: What still uses the block layer?
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On Mon, Oct 15, 2007 at 02:29:45PM +0100, Alan Cox wrote:
> > You can pull a Model and Serial number via hdparm -i, but it's not as
> > easy to manipulate as a fixed-length MAC address.  That's why people
> > tend to use filesystem UUID's.   
> 
> ATA8 at the moment looks set to add a true "MAC" or "WWN" type identifier
> to each device.. Right now model/serial is not always unique.

True, but most manufacturers try to make the serial number unique for
their own reasons (like warrantee service), and you can have
manufacturing errors with MAC assignment just as easily as you can
with serial numbers.

I still remember when SGI shipped MIT 20 SGI Indy pizza boxes that all
had the same MAC addresses (that we knew about --- we found out
because all 20 were installed on the same subnet).  That was a mildly
entertaining bug to track down....  especially since IIRC, Irix at the
time didn't print warning messages when someone else with a different
IP addresses responded to your MAC address.

   						- Ted
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