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    RE: SCSI Format/Copy CDB support




    That would be a mistake. It may affect commands intended to be dropped.

    If the window has moved past CmdSN you DO NOT reissue the command (that is clear in the text).

    Julo


    "Amir Shalit" <amir@astutenetworks.com>

    28-01-02 19:35

           
            To:        Julian Satran/Haifa/IBM@IBMIL
            cc:        
            Subject:        RE: SCSI Format/Copy CDB support

           


    Julo,

    We only need to ADD a single line to section 2.2.2.1 as follows:

    "CmdSN must change if the ExpCmdSN/MaxCmdSN window has moved."

    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."

    Amir

    From David Black:

    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:
    Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent:
    Sunday, January 27, 2002 9:17 PM
    To:
    Amir Shalit
    Subject:
    RE: SCSI Format/Copy CDB support


    Amir,


    A carefull reading of the spec will enable you to see that things are covered.

    I do not plan to add text - it only creates new sources of errors.


    Julo


    "Amir Shalit" <amir@astutenetworks.com>
    Sent by: owner-ips@ece.cmu.edu

    26-01-02 20:14

           
           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
    >
    >
    >
    >
    >
    >
    >








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