What we do is refer to drives by world wide number, until it hits the
Fiber channel HBA driver, at which time the WWN is exchanged for the
current ALPA (target id) -- this way everything always works!
Granted that refering to a drive as /dev/fc/w887384834,0 isn't pritty, but
is reliabe, and then because this name is always the same you can create a
symoblic link to it that is pritty and friendly.
The catch is that the computer idustry in moving into Storage Area
Networks (SANS -- probably knew that -- but I have been geting into
trouble lattly). And all of these networkds (e.g. firewire, usb, fibre
channel, infiniband...) all have some sort of dynaimic addressing
mechanism. And if we are truely embrassing the idea of a SAN then we need
to have friendly OS's on the SAN that don't write all over each others
labels.
Imagion that in the future that there might be an ANSI standard filesystem
and an ANSI standard partition, which are connected to a heterogenious
SAN. But then NT goes and writes a label on the disk, then Solaris goes
and over writes a small part of the NT label with it's own label, and then
Linux comes along and over writes both of their labels with its own label.
The nice thing about WWN's is that it allows OS's to do this book keeping
in a heterogenious network without these problems.
But we have to thing about storage from a new paradigm, one in which all
forms of storage are removable (in a sense) and one in which the path to
its location can change. In the old paradigm we could think of a drive
being located at host1 bus2 target3, but now all of that is changing,
things come and go and change paths.
But devfs allow linux to address these issues, and I think that this is a
crittical moment in history where we can prepare linux for the future --
but we have to try and guess what the future holds. Fortunatly we have
people like Richard Gooch that are willing to sink time into such
ventures.
Rodger Wilson
Target and SCSI Drivers (Sun Microsystems, Inc.)
DIRECT: (303) 272-8252 HOME: (303) 499-9498
FAX: (303) 272-7793 CELL: (303) 669-7955
PAGER: (303) 203-8561 EMAIL: Rodger.Wilson@sun.com
On Fri, 28 Apr 2000, Peter Svensson wrote:
> On Thu, 27 Apr 2000, Richard Gooch wrote:
>
> > I see no reason we can't have /dev/scsi/identifiers/ as well.
>
> And even for disks it makes sense. You want to mke2fs (or your filesystem
> of choise) the correct physical disk. You cannot really depend on the
> label in that situation, but a WWN sounds like just what is needed.
>
> Peter
> --
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> <petersv@df.lth.se> !
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> Remember, Luke, your source will be with you... always...
>
>
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