Subject: Re: iSCSI: naming/LUN views

From: "Jim Hafner" <[email-masked]>
Date: Tue, 27 Feb 2001 11:04:36 -0800

Pierre,

In my view, one should get the same LU view in your situation because there
is effectively no other information by which the target might present a
different view.  Namely, the target (that creates/enforces the view) is the
entity scoped by the TargetWWUI.  It uses the Initiator WWUI to construct
that LU view.  That might be constructed by rules established via SCSI
access controls (and yes, the InitiatorWWUI is the right mapping to
TransportID though that has not been formalized anywhere yet).

This has some interesting implications.  Within the context of a single
SESSION established through multiple connections, there is only the one I_T
nexus.  But we can also establish multiple sessions between the same
InitiatorWWUI and TargetWWUI.  As far as access controls are concerned, the
views should be identical.  As for other properties of I_T nexus', e.g.,
reservations, the jury is still out.

Jim Hafner

Pierre Labat <[email-masked]>@ece.cmu.edu on 02-27-2001 10:38:26 AM

Sent by:  [email-masked]

To:   [email-masked]
cc:
Subject:  iSCSI: naming/LUN views

Mark (Bakke),

After going through the naming/discovery drafts,
a question came to my mind:

Does several connections flowing through
several portals but using  the same initiator WWUI
and target WWUI will see the same thing on the target?
I mean by same thing: same LUs associated to the same LUNs.

I guess that the initiator WWUI acts as an transportID (SCSI access
control)
and gives the same LUs view independently of the portal used.
Is it the case?

If it is not the case, the entity that creates multiconnections
sessions
will need out of band information to know if the  2 portals can be used
for a same session or will have to do the  painfull job to compare the
LU views
from the two portals with no guarantee that the views could not change
in the future.

Regards,

Pierre

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From: Mark Bakke <[email-masked]>
Date: Tue, 27 Feb 2001 14:00:46 -0600

Pierre-

Sorry I took so long to reply; for some reason, I didn't receive
your original message from the reflector.

I agree with all of Jim's comments, but would state this one
more strongly:

  A TargetWWUI MUST present exactly the same LU view to an
  InitiatorWWUI regardless of the portal on which it is accessed.

This means that we have a method of identification at the target
level, which we were missing (at least as a standard) from FC and
parallel SCSI.

This was our intent, and would solve the problem you stated of
having to compare views.  Perhaps we should add this statement
to the document.

--
Mark

-- 
Mark A. Bakke
Cisco Systems
[email-masked]
763.398.1054

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From: Pierre Labat <[email-masked]>
Date: Tue, 27 Feb 2001 13:44:11 -0800

Mark,Jim,

> level, which we were missing (at least as a standard) from FC and

Perfect.

> having to compare views.  Perhaps we should add this statement

Yes, i think it has to be said explicitely.

Regards,

Pierre