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Date:      Wed, 27 Apr 2011 01:04:52 +0200
From:      Mikael Fridh <frimik@gmail.com>
To:        Doug Barton <dougb@freebsd.org>
Cc:        freebsd-fs@freebsd.org, Alexander Best <arundel@freebsd.org>, Alexander Motin <mav@freebsd.org>
Subject:   Re: Why not just name the cam-ata devices the same as the old names?
Message-ID:  <BANLkTikFHLaQ=Vrt9UhyJdo5ELm522OZjA@mail.gmail.com>
In-Reply-To: <4DB70F13.6060002@FreeBSD.org>
References:  <4DB70949.6090104@FreeBSD.org> <20110426182017.GA92471@freebsd.org> <4DB70F13.6060002@FreeBSD.org>

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On Tue, Apr 26, 2011 at 8:29 PM, Doug Barton <dougb@freebsd.org> wrote:
> On 04/26/2011 11:20, Alexander Best wrote:
>>
>> personally i think maintaining backwards compatibility to adX is
>> unnecessary.
>> the adaY names will appear in 9.0. anybody upgrading to a major new
>> release
>> should expect to adjust certain config files and it's not really a big
>> deal.
>
> The problem is that this is not a realistic point of view. When there are
> very good reasons to make changes like this we do it, but there has to be a
> *really* good reason. Something like this which is going to cause systems to
> fail when users reboot them better have an overwhelmingly good reason.
>
> And yes, I get that from a developer perspective we expect users to read
> documentation, they should know what they are doing before they do it, blah
> blah blah. Like I said, this is NOT a reasonable perspective, and screwing
> the users over in this way is going to do nothing but damage FreeBSD's
> reputation. Need I remind everyone on this list of the problems that have
> resulted from removing support for "dangerously dedicated" disks? Now
> imagine that 100 times over.

Regarding this documentation I gladly read since it's usually
well-written - I would very much like for the recommendation to be not
to change from adX to adaY, but instead tell me to change to using
labels. Is there something missing in the Handbook on using labels or
are there some gotchas I'm not thinking about?
http://www.freebsd.org/doc/en/books/handbook/geom-glabel.html

There was a post recently on freebsd-current: "Re: Switch from legacy
ata(4) to CAM-based ATA"  saying that "labels and stacked geoms do not
work well together", but other than that I have no idea what to watch
out for.

The only fear I have is that I will one day insert a disk from a
similar system with a clashing label such as "root" or "data" and it
would mess up the boot, but I would have no one to blame but myself
and I could easily reduce that risk by using a more host-unique
labelling scheme, such as 'hostymdroot', 'hostymddata' etc (ymd = year
month day). Maybe I'm naive and misinformed and really should be more
paranoid?

Are labels such a perilous affair that you can't just start
recommending them and/or default to them? I don't have many FreeBSD
systems yet but all of them are using labels in fstab for all disks,
gmirrors or usb flash drives and so far it served me well when I had
to move disks and usb boot sticks between different and/or failing
motherboards and controllers.

Mikael



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