RE: SCSI URL scheme [WAS: Re: iSCSI: 2.2.6. Naming & mapping]

["John Hufferd/San Jose/IBM" <hufferd@us.ibm.com>]

Howard Green,
I just put in a couple of note asking some questions about this.  (The
thread was changed to :SCSI URL scheme.)  Those thoughts and question might
have some barring here.  In any event, assuming your idea is  valuable, I
think you are talking about major changes to the CDB structure, and that
should be deferred to the T10 committee.

.
.
.
John L. Hufferd


Howard Green <hgreen@Brocade.COM>@ece.cmu.edu on 10/03/2000 08:35:15 AM

Sent by:  owner-ips@ece.cmu.edu


To:   "'Raghavendra Rao'" <jpr@divyaroot.India.Sun.COM>, ips@ece.cmu.edu
cc:
Subject:  RE: SCSI URL scheme [WAS: Re: iSCSI: 2.2.6. Naming & mapping]



I know that the following is kind of a radical question to ask, but has the
time arrived to toss out LUNs as a means of identifying logical units, in
favor of simply using the logical units' WWNs directly?

Currently, an IU containing a SCSI command identifies the target logical
unit by a Logical Unit Number. Back in the good ol' days, LUNs were small
integers contained directly in each CDB, and were (in practice, if not in
theory) a simple index assigned to a specific logical unit throughout its
life.

SCSI has obviously evolved to a far more sophisticated state of affairs.
The LUNs have grown to 64 bits, opaque used to identify a logical unit can
vary over time, relative to the interface used, and as a function of the
initiator's identity.

The WWNs I've seen used to identify logical units currently range from 64
to 128 bits,

> -----Original Message-----
> From: Raghavendra Rao [mailto:jpr@divyaroot.India.Sun.COM]
> Sent: Tuesday, October 03, 2000 10:56 AM
> To: ips@ece.cmu.edu
> Subject: Re: SCSI URL scheme [WAS: Re: iSCSI: 2.2.6. Naming & mapping]
>
>
>
> > out-of-band).  I don't see the point of the initiator
> sending its "view" to
> > the target at any point.  If the initiator sends an
> incorrect view, you've
> > just created an error scenario which needs additional definition.
>
> Well, to extend what Julian said further, the initiator could
> ask the target
> for a LUN value corresponding to a WWN as part of the
> authentication process,
> instead of presenting its view - whether right or wrong. But
> something like
> this needs to be done as there is no easier/faster way to
> translate a LU WWN
> to a LUN value.
>
> This may also help in building an authentication method for a
> LU access where
> no such thing exists today ?
>
>
> > case, the target will send its "view" for that initiator in
> REPORT LUNS
> > SCSI command after login (which is actually the layer that
> cares about the
> > LUN Map at all anyway).
> >
>
> This will be a problem if the storage controller has a lot of
> LUNs. Since
> REPORT LUNS only returns a list of LUNs, the initiator still
> has to send an
> INQUIRY (page 83) request to each LU to to find a matching LU
> WWN (or until
> a matching WWN is found).
>
> -JP
>