All SCSI 3 and (I think) most SCSI 2 devices have a unique identifier that
is burned into their epprom to help identify them. Within a SAN we might
have millions of drives comming and going, and we need to be able to
identify drives by something other than Target id. Because the target id
could change on us dynamically.
Also we need to be able to uniquely identify a drive because it might be
attached to a computer through 1, 2, 3 .... io cards within the system.
This way if someone was to trip over a connection to a drive, the system
can easily identify that the *SAME* device is accessable through a
different controller.
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 Thu, 27 Apr 2000, Richard Gooch wrote:
> Rodger Wilson writes:
> > I quickly read through the paper, and came up with a question.
> >
> > Talking about persistence -- what about scsi device that dynamically
> > change their target id's (i.e. fiber channel). How do we make sure that
> > we continue to refernce disk1 as disk1. With a possible 16 million
> > devices this could get hairy.
> >
> > If we are wanting to have multi-pathed access to a drive it would be
> > nice to have that reflected in the dev tree, but it would also be
> > nice to easily refer to a unique drive, via WWN. By using the World
> > Wide Number we can make sure that we know exactly which drive we are
> > refering to.
>
> If by WWN you mean UUID (or a human-friendly label), then that's
> coming. Right now this is done in mount(8), so it won't work for the
> root FS. Check the linux-kernel archives for my planned solution to
> this.
>
> Regards,
>
> Richard....
> Permanent: rgooch@atnf.csiro.au
> Current: rgooch@ras.ucalgary.ca
>
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