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    Re: questions on the mapping in iSCSI



    
    
    I sent the response to the list a while ago. But here I attach it again
    and again Good Luck, Julo
    
    ----------------------------------
    
    
    Julian Satran
    21/07/2000 09:42
    
    To:   ips@ece.cmu.edu
    cc:
    From: Julian Satran/Haifa/IBM@IBMIL
    Subject:  Re: questions on the mapping in iSCSI  (Document link: Julian
          Satran - Mail)
    
    Bill,
    
    SRA's are returned by the target - the initiator only provides the
    descriptors;
    the idea is to let the target organize them as it sees fit (e.g., store the
    strings only once even if they originate from different initiators).
    
    I expect you would want to do as much work as possible and explore all
    descriptors.
    However finding out that a descriptor is bad can happen even after mapping.
    I refrained in fact specifying when will the name-to-address mapping be
    done (lazy or eager).
    
    I assume that unmapping should not have any effect on outstanding I/O - but
    I will make
    a not to clarify this point.
    
    Good luck with the implementation and thanks,
    Julo
    
    Bill Main <wmain@gis.net> on 21/07/2000 00:34:30
    
    Please respond to bill.main@bigfoot.com
    
    To:   ipSCSI list <ips@ece.cmu.edu>
    cc:    (bcc: Julian Satran/Haifa/IBM)
    Subject:  questions on the mapping in iSCSI
    
    
    
    
    Folks-
        Been working on trial implementation of iSCSI as it seems to me the
    easiest way to find loose threads in a new spec.
    
    couple of items have showed up so far:
    
        Question with regard to the mapping. I see latest spec descriptors
    that move from initiator to host but the response to mapping has little
    data in it other than status. Who generates the SRA's for the host to
    use.
    
    Are the SRA's part of the descriptor and the host is therefore informing
    the target what LUN id it will use for this "view"?
    
    Or should the SRA be returned from the target to inform the host what
    SRA to use to reach the desired view? If so the data layout needs
    updating to accommodate this.
    
        Next, multiple descriptors are allowed in the map command. What
    action should be taken if one is bad? Do the others and respond with
    failure or disallow others from succeeding? or should we limit the map
    command to single descriptor? I am thinking also of the poor sys admin
    trying to fix a broken mount command.
    
        Next, on the unmapping. What happens when an unmapping is done and
    outstanding IO's are pending on the device? in flight? Does the target
    can them or let them complete?
    
        It is not clear, but I presume the response to the unmap occurs
    after the IO's are either completed or aborted and abort is confirmed by
    the hardware at the target end. Is this correct?
    
        -Bill
    
    
    
    ___________________________
    
    Bill Main <wmain@gis.net> on 21/07/2000 17:07:52
    
    Please respond to bill.main@bigfoot.com
    
    To:   Julian Satran/Haifa/IBM@IBMIL
    cc:
    Subject:  questions on the mapping in iSCSI
    
    
    
    
    Julian-
         I have not had any responses to the spec question so I thought I would
    ask the author directly.
    
         I do have to say however that the state table on this has come
    together
    very nicely in general. Although I am not done yet, it seems be a well
    laid out spec. My compliments!
    
         -Bill
    
    Folks-
        Been working on trial implementation of iSCSI as it seems to me the
    easiest way to find loose threads in a new spec.
    
    couple of items have showed up so far:
    
        Question with regard to the mapping. I see latest spec descriptors
    that move from initiator to host but the response to mapping has little
    data in it other than status. Who generates the SRA's for the host to
    use.
    
    Are the SRA's part of the descriptor and the host is therefore informing
    the target what LUN id it will use for this "view"?
    
    Or should the SRA be returned from the target to inform the host what
    SRA to use to reach the desired view? If so the data layout needs
    updating to accommodate this.
    
        Next, multiple descriptors are allowed in the map command. What
    action should be taken if one is bad? Do the others and respond with
    failure or disallow others from succeeding? or should we limit the map
    command to single descriptor? I am thinking also of the poor sys admin
    trying to fix a broken mount command.
    
        Next, on the unmapping. What happens when an unmapping is done and
    outstanding IO's are pending on the device? in flight? Does the target
    can them or let them complete?
    
        It is not clear, but I presume the response to the unmap occurs
    after the IO's are either completed or aborted and abort is confirmed by
    the hardware at the target end. Is this correct?
    
        -Bill
    
    
    
    


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