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Date:      Tue, 27 Jun 2006 13:21:05 +0200
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Peter Jeremy <peterjeremy@optushome.com.au>
Cc:        Poul-Henning Kamp <phk@phk.freebsd.dk>, freebsd-arch@freebsd.org
Subject:   Re: Accessing disks via their serial numbers.
Message-ID:  <20060627112105.GC21661@garage.freebsd.pl>
In-Reply-To: <20060627080312.GB714@turion.vk2pj.dyndns.org>
References:  <20060626171035.GE12511@garage.freebsd.pl> <56651.1151347579@critter.freebsd.dk> <20060627080312.GB714@turion.vk2pj.dyndns.org>

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On Tue, Jun 27, 2006 at 06:03:12PM +1000, Peter Jeremy wrote:
> On Mon, 2006-Jun-26 18:46:19 +0000, Poul-Henning Kamp wrote:
> >>> 4.	It prevents cold-state swapout of disk drives.
> >>
> >>Why?
> >
> >Because /etc/fstab contains the serial number of the disk you just
> >junked and the new one has a different serial number.
>=20
> I've used a couple of OSs that derived their logical disk name (ie
> /dev/disk/dsk5) from the WWID by keeping a magic database to map
> the WWID to the name.  None of them have good solutions to telling
> the OS that WWID-x has died and I want WWID-y to now map to the same
> logical device as WWID-x used to.
>=20
> Actually having the WWID (or similar) as the logical name would make
> handling a disk swap really nasty.
>=20
> Stating that the sysadmin knows about the change doesn't address the
> issue:  The sysadmin changed the device because the old one failed.
> There may or may not have been advance notice of the replacement.

I'm not saying it solves all problems, but it is very useful in certain
situations, where what you mentioned is not the case.

For software RAID you still has to somehow say that this driver replaced
that one.

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

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