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    RE: iSCSI: more on StatRN



    
    
    Recovery does not depend on numbering. This should be clear even from the
    current draft if you care
    to read it.
    
    Julo
    
    "Douglas Otis" <dotis@sanlight.net> on 23/10/2000 20:20:48
    
    Please respond to "Douglas Otis" <dotis@sanlight.net>
    
    To:   csapuntz@cisco.com, Prasenjit Sarkar/Almaden/IBM@IBMUS
    cc:   ips@ece.cmu.edu
    Subject:  RE: iSCSI: more on StatRN
    
    
    
    
    Costa,
    
    Although I had suggested a keep-alive recommendation several months ago,
    depending on the OS to detect TCP failure is not likely to provide timely
    detection.  Perhaps 3 lost echoes if no communication at 10 second
    intervals
    would establish a 40 second fail/recovery period.  A justification for
    statRN would be with respect to recovery on a different connection.  iSCSI
    transport layer on top of a TCP transport layer to support the SCSI
    transport layer.  (How does iSCSI work on a single connection without a
    command numbering?)  This iSCSI transport depends on command, data, and
    response numbering.  The difficult aspect of recovery is created with an
    command, data and response allegiance requirement on adapters.  Can a
    failed
    portion of a connection recover over a different adapter and thus violate
    adapter allegiance?
    
    Doug
    
    
    > > While I know the values for certain operating systems, I would
    > like to hear
    > > from
    > > people who can assert confidently that the TCP fail connection
    > time < SCSI
    > > command failure time.
    >
    > Prasenjit,
    >
    > You bring up a good point.
    >
    > However, iSCSI is the master of the TCP stack; it can abort the TCP
    > connection at any time for any reason. It doesn't need to wait for
    > TCP to fail; iSCSI can timeout and close the TCP connection.
    >
    > The question becomes then: what performance on the TCP virtual circuit
    > is so unacceptable that iSCSI should tear down the TCP connection
    > and try to establish a new one?
    >
    > As such, I don't believe the TCP-iSCSI interface has any effect on
    > the motivation for statRNs.
    >
    > -Costa
    >
    
    
    
    
    


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