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Date:      Tue, 14 Jul 2009 10:30:30 +1000
From:      Peter Jeremy <peterjeremy@optushome.com.au>
To:        Scott Long <scottl@samsco.org>
Cc:        "Carlos A. M. dos Santos" <unixmania@gmail.com>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r195534 - in head: etc/mtree include lib/libcam sbin/camcontrol share/man/man4 sys/cam sys/cam/ata sys/cam/scsi sys/conf sys/dev/advansys sys/dev/ahci sys/dev/aic7xxx sys/dev/amd sys/de...
Message-ID:  <20090714003030.GE43362@server.vk2pj.dyndns.org>
In-Reply-To: <4A5A98FA.3050208@samsco.org>
References:  <37131.1247214217@critter.freebsd.dk> <4A56FC7C.8060107@samsco.org> <e71790db0907121809k3c66243fxd039fc67b41ab1d@mail.gmail.com> <4A5A98FA.3050208@samsco.org>

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On 2009-Jul-12 20:16:26 -0600, Scott Long <scottl@samsco.org> wrote:
>Another solution is to just bite the bullet and do what I've ultimately
>wanted to do with disk device names, and create 'diskX' aliases for all
>direct-access block devices.  This would affect hard disks, memory
>sticks, logical disks like g_raid things, and things that look like hard
>disks.

Having removable devices in the same space as fixed devices _will_ bite
users when they accidently reboot without pulling out their memory stick
and find that their disk numbering is all changed.  Wiring physical
addresses to names might help but can need manual configuration.

I suspect a "one size fits all" approach isn't going to satisfy
everyone.  Someone with a bog standard desktop with one HDD on SATA
channel 0 who occasionally plugs in a USB stick has significantly
different needs to someone running a server with multiple SATA port
multipliers and multi-pathed fibre-channel who has a USB stick
permanently installed for booting.  (Note that physical cXtYdZ
approaches don't mesh cleanly with multi-pathing).

IMHO, you need a provision to apply user-selected labels to disks and
then reference them via those labels (with some sort of fallback to
handle clashes).  WWN or system-generated labels are too unfriendly to
use.  (And one of our HP support techs related a story where a
customer was having some really strange problems on a Tru64 system
which he eventually tracked down to two of the disks having the same
WWID - which he agrees should never occur).

--=20
Peter Jeremy

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