Re: iSCSI: Login Redirect

[John Hufferd <hufferd@us.ibm.com>]

Extending my own note... I also believe it would be wrong to set a minimum number of guaranteed redirects.  This is because, I expect several system vendors to use iSCSI as a DAS technology as well as SAN technology.  (Similar to the way a number of vendors "Racked" their FC external Raid controllers together with the server as a Direct Connection.)  When used in this manner the customer does not even need to think about the system being on a SAN.  Yet the Storage/System Vendor could use the very same Raid controller, which they use in a SAN, as a direct attachment to the Server in a RACK.  In this environment if any redirect occur, it might be considered a error.

So in the above DAS environment having a minimum is, IMHO, not approprate.

Instead, the permissible number of redirects is an administrative or implementation setting. 
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John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/System Group, San Jose CA
Main Office: (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688
Alt Office: (408) 997-6136, Cell: (408) 499-9702
Internet Address: hufferd@us.ibm.com

John Hufferd/San Jose/IBM@IBMUS Sent by: owner-ips@ece.cmu.edu 07/16/2003 05:07 AM

To:        "Mallikarjun C." <cbm@rose.hp.com>         cc:        ips@ece.cmu.edu, "Lakshmi Ramasubramanian" <nramas@windows.microsoft.com>, owner-ips@ece.cmu.edu         Subject:        Re: iSCSI: Login Redirect

I think that Mallikarjun, has correctly stated what should/should not be done here.  The number of times that an initiator may permit its connection request to be redirected is an initiator design consideration.  It is inappropriate to have a hard limit built into the protocol.
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John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/System Group, San Jose CA
Main Office: (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688
Alt Office: (408) 997-6136, Cell: (408) 499-9702
Internet Address: hufferd@us.ibm.com

"Mallikarjun C." <cbm@rose.hp.com> Sent by: owner-ips@ece.cmu.edu 07/15/2003 10:14 AM

To:        "Lakshmi Ramasubramanian" <nramas@windows.microsoft.com>, <ips@ece.cmu.edu>        cc:                Subject:        Re: iSCSI: Login Redirect

If this mis-direction is going on to different portals within
the same target node, I would think that it implies a serious
configuration issue within the target node because it either
does not have a global node-level view of the iSCSI service
it offers, or the situation is changing too rapidly to be correct.

If on the other hand, this mis-direction is forcing an 
initiator to shuttle to different target nodes, it usually implies a
lack of a consistent SAN-level view among the target nodes
that are supposed to be doing cooperative redirection (which
is what the feature was meant for).

In either case, I tend to think that the issue is one of implementation/
configuration and placing hard limits on the # of redirections in
the spec is neither reasonable nor enforceable.   I believe that the 
spec doesn't preclude implementations from having a limit (for ex., the 
initiator iSCSI may decide to give up the chase after X attempts and 
report a failure to its ULP).
--
Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions
Hewlett-Packard MS 5668 
Roseville CA 95747
cbm@rose.hp.com

----- Original Message ----- 
From: "Lakshmi Ramasubramanian" <nramas@windows.microsoft.com>
To: <ips@ece.cmu.edu>
Sent: Tuesday, July 15, 2003 8:51 AM
Subject: iSCSI: Login Redirect


When a target is moved (Temporary or Permanent), target
sends an appropriate status code and gives the new target
address. Is there a limit on the number of times a target
can redirect login? If not, should we have one?

   Initiator logs into Portal A. 
   Target redirects to Portal B.
   Initiator logs into Portal B. 
   Target now redirects to Portal C.
   And so on...

Should we have an upper limit on the number of times a target
can redirect the login?

thanks!
-lakshmi