RE: SCSI Format/Copy CDB support

[Black_David@emc.com]

The CmdSN window should take care of the "long time"
issue - once the Window (ExpCmdSN/MaxCmdSN) has moved
past a particular CmdSN, the initiator knows that the
target successfully received the command, and reissuing
the command with the same CmdSN would be an error.
Julian - please add a suitable clarification to the
next version of the spec.

Thanks,
--David

> -----Original Message-----
> From: Amir Shalit [mailto:amir@astutenetworks.com]
> Sent: Saturday, January 26, 2002 1:15 PM
> To: Black_David@emc.com
> Cc: ips@ece.cmu.edu
> Subject: RE: SCSI Format/Copy CDB support
> 
> 
> David,
> 
> I agree. Lets clarify it in the spec. We also must make
> sure that iSCSI doesn't reissue a command due to connection
> drop that happened a "long time" after the command was 
> originally issued.
> 
> Amir
> 
> -----Original Message-----
> From: Black_David@emc.com [mailto:Black_David@emc.com]
> Sent: Saturday, January 26, 2002 12:32 AM
> To: amir@astutenetworks.com
> Cc: ips@ece.cmu.edu
> Subject: RE: SCSI Format/Copy CDB support
> 
> 
> Ah, I see the confusion.  In that section, "reissued"
> refers to reissuing a command due to holes in the command
> sequence (e.g., digest failure, connection drop).  In
> the scenario of interest, the command is not being
> reissued by iSCSI - SCSI is aborting the old command
> based on the task tag and issuing a new command which
> will get a new CmdSN (iSCSI will probably have long since
> forgotten the CmdSN assigned to the original command).
> A sentence or two to clarify this wouldn't hurt.
> 
> --David
> 
> > -----Original Message-----
> > From: Amir Shalit [mailto:amir@astutenetworks.com]
> > Sent: Friday, January 25, 2002 7:03 PM
> > To: Julian Satran
> > Cc: ips@ece. cmu. edu (E-mail); owner-ips@ece.cmu.edu
> > Subject: RE: SCSI Format/Copy CDB support
> > 
> > 
> > Julo,
> > 
> > I was talking about initiator aborting the command
> > ,say two hours after it was sent, and than reissue
> > the same command with the old CmdSN (according to
> > the spec).
> > 
> > I agree with you that the spec covers all other cases
> > since once a command is delivered, CmdSN doesn't
> > matter much and ITT or TTT are used to match the
> > task.
> > 
> > Amir
> > 
> > -----Original Message-----
> > From: owner-ips@ece.cmu.edu 
> [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> > Julian Satran
> > Sent: Friday, January 25, 2002 2:14 PM
> > To: Amir Shalit
> > Cc: ips@ece. cmu. edu (E-mail); Julian Satran; owner-ips@ece.cmu.edu
> > Subject: RE: SCSI Format/Copy CDB support
> > 
> > 
> > 
> > Amir,
> > CmdSN is completely secondary in abort task.
> > The main element is the Initiator Task Tag.
> > If ITT is not found at abort then the target, under some 
> > cirscumstances,
> > will look for a hole at CmdSN to fill it or will answer 
> > negatively the Task
> > Abort.
> > 
> > Julo
> > 
> > 
> > 
> >                     "Amir Shalit"
> >                     <amir@astutenet       To:     Julian
> > Satran/Haifa/IBM@IBMIL
> >                     works.com>            cc:     "ips@ece. cmu. edu
> > \(E-mail\)" <ips@ece.cmu.edu>,
> >                                            <owner-ips@ece.cmu.edu>
> >                     25-01-02 18:49        Subject:     RE: 
> > SCSI Format/Copy
> > CDB support
> > 
> > 
> > 
> > 
> > 
> > 
> > Julo,
> > 
> > I agree with you on (2).
> > 
> > Section 2.2.2.1 is saying:
> > "A numbered iSCSI request will not change its allocated CmdSN
> > regardless of the number of times and circumstances in which it is
> > reissued."
> > 
> > A long duration SCSI command may be aborted by a task management
> > command and than reissued by iSCSI with a stale CmdSN.
> > 
> > Amir
> >      -----Original Message-----
> >      From: owner-ips@ece.cmu.edu 
> > [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> >      Julian Satran
> >      Sent: Friday, January 25, 2002 1:21 AM
> >      To: Amir Shalit
> >      Cc: ips@ece. cmu. edu (E-mail); owner-ips@ece.cmu.edu
> >      Subject: Re: SCSI Format/Copy CDB support
> > 
> > 
> >      Amir,
> > 
> >      The draft says in several places that CmdSN is not 
> > important after the
> >      task gets to SCSI.
> >      On 2 yes you might be right but that is purely an 
> implementation
> >      issue. Format commands do not time-out
> >      at SCSI level and iSCSI has no cause to e "nervous" - 
> nothing is
> >      expected.
> > 
> > 
> >      Julo
> > 
> > 
> > 
> > 
> >    "Amir Shalit"
> >    <amir@astutenetworks.com>              To:        
> > "ips@ece. cmu. edu
> >    Sent by: owner-ips@ece.cmu.edu \(E-mail\)" <ips@ece.cmu.edu>
> >                                           cc:
> >                                           Subject:        
> > SCSI Format/Copy
> >    25-01-02 02:10                 CDB support
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> >      I see a few problems in implementing the format/copy 
> > commands over
> >      iSCSI
> > 
> >      1) CmdSN may wrap between command and response 
> (assuming multiple
> >      LUNs)
> > 
> >      2) iSCSI keepalive NOPs may be required to keep the 
> > connection open
> >      during format
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
>