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    RE: ISCSI: Unsolicited data in draft v12



    John,
    
    It's not so much an implementation problem but one resource management
    problem in that if unsolicited data has been negotiated then target MUST
    pre-allocate buffers with which to store the unsolicited when it arrives.
    The target implementors will decided whether they want to use unsolicted
    data and take the buffer resource hit in doing so.  However, if they do wish
    to take this hit but the initators decide not to use unsolicited data (even
    though they have negotiated to use it) then there is potientially a lot of
    valuable buffer resources tied in up for unsolicited data but which is not
    being used.
    
    Matthew
    
    -----Original Message-----
    From: John Hufferd [mailto:hufferd@us.ibm.com]
    Sent: Monday, April 08, 2002 11:13 AM
    To: BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)
    Cc: 'Julian Satran'; Rod Harrison; ips@ece.cmu.edu;
    owner-ips@ece.cmu.edu
    Subject: RE: ISCSI: Unsolicited data in draft v12
    
    
    
    Please explain, why an initiator deciding to not send unsolicited data for
    a specific command causes an implementation problem.  That was not clear
    from your statements.  You still need the R2T capability, so what is lost?
    
    .
    .
    .
    John L. Hufferd
    Senior Technical Staff Member (STSM)
    IBM/SSG San Jose Ca
    Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
    Home Office (408) 997-6136, Cell: (408) 499-9702
    Internet address: hufferd@us.ibm.com
    
    
    "BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)" <matthew_burbridge@hp.com>
    @ece.cmu.edu on 04/08/2002 10:25:55 AM
    
    Sent by:    owner-ips@ece.cmu.edu
    
    
    To:    "'Julian Satran'" <Julian_Satran@il.ibm.com>, Rod Harrison
           <rod.harrison@windriver.com>
    cc:    ips@ece.cmu.edu, owner-ips@ece.cmu.edu
    Subject:    RE: ISCSI: Unsolicited data in draft v12
    
    
    
    I must express my concern on this issue.  From a target point of view once
    it has negoiated the use of unsolicited data it has to allocate buffer
    space
    for that unsolicited data.  Now depending on the various parameters this
    may
    be a sizeable chunk of valuable resources which it is making available.
    Now
    if the decision to use unsolicited data is being moved from a per session
    to
    per task basis (which is what this change effectively does) then it puts an
    awful lot of resource overhead on the target which may never be used.
    
    For the reasons above I propose that we do not relax the v12 restriction
    and
    keep it as:
    
    "An iSCSI initiator MUST send as unsolicited data either the negotiated
    amount or all the data if the total amount is less than the negotiated
    amount for unsolicited data."
    
    Matthew Burbridge
    Principal Engineer
    NSAS-Bristol
    Hewlett Packard
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Monday, April 08, 2002 9:36 AM
    To: Rod Harrison
    Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
    Subject: Re: ISCSI: Unsolicited data in draft v12
    
    
    
    OK - Julo
    
    
    "Rod Harrison" <rod.harrison@windriver.com>
    Sent by: owner-ips@ece.cmu.edu
    08-04-02 14:52
    Please respond to "Rod Harrison"
    
            To:        <ips@ece.cmu.edu>
            cc:
            Subject:        ISCSI: Unsolicited data in draft v12
    
    
    
    
    
                    I propose we slightly relax the new restriction in draft
    v12
    that the
    initiator MUST send the maximum permissible amount of unsolicited data. I
    suggest we change the rule to allow the initiator to either send no
    unsolicited data, or the maximum permissible.
    
                    There is no difficulty for the target here since the lack
    of
    unsolicited
    data will be clearly indicated by a command PDU with F bit set and
    dataSegLen=0. The target will have all the information it needs to
    immediately issue R2Ts as appropriate.
    
                    I believe the initiator should be able to make a policy
    decision on which
    individual commands should be sent with unsolicited data and which should
    not.
    
                    In draft 11.91 section 2.2.4 I suggest we change
    
    "An iSCSI initiator MUST send as unsolicited data either the negotiated
    amount or all the data if the total amount is less than the negotiated
    amount for unsolicited data."
    
                    to something like
    
    "An iSCSI initiator MAY choose to send no unsolicited data with a command,
    or if any unsolicited data is sent it MUST be either the negotiated amount
    or all the data if the total amount is less than the negotiated amount for
    unsolicited data."
    
                    - Rod
    
    
    


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