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    iSCSI: Need to Kill Session from Surviving Node



    
    There is a related problem that I think we need to address, and that is --
    the case where the Storage Controller is an Active-Active Fail-Over unit
    with very little state shared between the Storage Controller Nodes.  (I
    think a number of you folks have told me that you are planning such a
    design.)  This would mean that a specific initiator OS (WWUI) would have
    separate sessions between the Nodes.  At fail-over, the Take-Over Node will
    want to cause the Initiator, to Stop messing around with the Failing node
    ASAP, and start using the existing session, or start a new session with the
    Take_Over Node.  The Initiator, will normally just time-out the TCP/IP
    connection, and then turn the recovery over to the SCSI Layer. Then, when
    SCSI retries, iSCSI will either use the Session to the Surviving Node or
    Create a New Session to that Surviving Node.  The problem is, that this
    will take a longer time then a system might want.
    
    So the question: is there a way for a surviving Target Node to tell the
    Initiator to "Kill" the Session to the Failing Target Node?
    
    Comments?
    
    .
    .
    .
    John L. Hufferd
    Senior Technical Staff Member (STSM)
    IBM/SSG San Jose Ca
    (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
    Internet address: hufferd@us.ibm.com
    
    
    Julian Satran/Haifa/IBM@IBMIL@ece.cmu.edu on 03/14/2001 08:31:19 AM
    
    Sent by:  owner-ips@ece.cmu.edu
    
    
    To:   ips@ece.cmu.edu
    cc:
    Subject:  Re: iSCSI: Logout needs ISID
    
    
    
    
    
    Mark,
    
    If you have only one connection you are supposed to use a Login with the
    restart bit one - and achieve a similar effect as a Login/Logout - i.e.
    keep the session alive.  Even this might be a problem for a target that is
    so poor it has only one socket (even SNMP won't work there).  For this case
    the only way out is to drop the connection and hope the target will hear
    you (it probably won't -:)). The comment is the draft is a memento for
    implementers to keep looking for new connections always (even for a one
    connection target) but probably it does not come through clear enough.
    
    Regards,
    Julo
    
    Mark Bakke <mbakke@cisco.com> on 14/03/2001 18:17:14
    
    Please respond to Mark Bakke <mbakke@cisco.com>
    
    To:   Julian Satran/Haifa/IBM@IBMIL
    cc:   ips@ece.cmu.edu
    Subject:  Re: iSCSI: Logout needs ISID
    
    
    
    
    Julian-
    
    A target that does not support multiple connections per session
    will return "Initiator SID Error" when the login attempt is made.
    In this case, there is no way to log in, so there's no way to
    log out the old connection.  The initiator would be stuck waiting
    until the target's side of the connection times out and goes
    away, which could be a very long time.
    
    There is an open question within the MIB team about whether anyone
    needs to be able to kill connections or sessions from SNMP; however,
    I don't think that anyone will want to use SNMP as part of error
    recovery.
    
    --
    Mark
    
    julian_satran@il.ibm.com wrote:
    >
    > Josh,
    >
    > No command, including logout, can be sent without a login.
    > The complete scenario is:
    >
    > -open a new connection
    > -login in the same session as the old connection (this has the ISID &
    TSID)
    > -logout the old connection
    > -recover commands
    >
    > You are not supposed to be able to kill a session from outside (at least
    > not an iSCSI defined mode).
    > You will need management support for that (SNMP?)
    >
    > Regards,
    > Julo
    >
    > Joshua Tseng <jtseng@NishanSystems.com> on 14/03/2001 17:09:48
    >
    > Please respond to Joshua Tseng <jtseng@NishanSystems.com>
    >
    > To:   Julian Satran/Haifa/IBM@IBMIL, ips@ece.cmu.edu
    > cc:
    > Subject:  RE: iSCSI: Logout needs ISID
    >
    > Julian,
    >
    > In 2.14, you state that a logout command can be
    > sent on a different connection to destroy a single-
    > connection iSCSI session.  If you have multiple
    > sessions ongoing, and the logout command is sent
    > on a different connection than the one used
    > to support the session that is to be killed, then
    > you will need ISID to distinguish the session that
    > you want killed.
    >
    > Regards,
    > Josh
    >
    > > -----Original Message-----
    > > From: julian_satran@il.ibm.com [mailto:julian_satran@il.ibm.com]
    > > Sent: Tuesday, March 13, 2001 9:57 PM
    > > To: ips@ece.cmu.edu
    > > Subject: Re: iSCSI: Logout needs ISID
    > >
    > >
    > >
    > >
    > > Josh,
    > >
    > > There is something I am missing. The Logout can be issued
    > > only after Login
    > > (authentication and the rest).
    > > The session is then implied.
    > >
    > > Regards,
    > > Julo
    > >
    > > Joshua Tseng <jtseng@NishanSystems.com> on 14/03/2001 03:56:45
    > >
    > > Please respond to Joshua Tseng <jtseng@NishanSystems.com>
    > >
    > > To:   Julian Satran/Haifa/IBM@IBMIL
    > > cc:   ips@ece.cmu.edu
    > > Subject:  iSCSI:  Logout needs ISID
    > >
    > >
    > >
    > >
    > > Julian,
    > >
    > > Section 2.14 states that the logout command may
    > > be sent on a second connection to clean up the
    > > a single connection iSCSI session.  If the reason
    > > code is 0 (close the session), then ISID is needed
    > > to identify the iSCSI session to close.
    > >
    > > Josh
    > >
    > >
    > >
    
    --
    Mark A. Bakke
    Cisco Systems
    mbakke@cisco.com
    763.398.1054
    
    
    
    
    
    
    


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Last updated: Tue Sep 04 01:05:20 2001
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