RE: iSCSI: Need to Kill Session from Surviving Node

["Somesh Gupta" <someshg@yahoo.com>]

Do you need both a "warm-reset" and a "cold-reset"?
The "warm-reset" seems to be an over-optimization.

Somesh

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Mallikarjun C.
> Sent: Wednesday, March 14, 2001 12:16 PM
> To: ips@ece.cmu.edu
> Subject: Re: 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?
>
> Assuming that the failing Node is still able to execute commands,
> a cold target reset from the Initiator to the failing node should "kill"
> all the sessions to it.
>
> The answer to two hosts configured in a failover configuration sharing
> a single Storage Controller Node is also the same.
>
> If it is active-active configuration, it appears to me that there's a
> need to somehow prompt the Initiator to doing the reset on a third party
> (Async PDU?).
>
> This is a reason why we'd still need target reset in iSCSI.
> --
> Mallikarjun
>
>
> Mallikarjun Chadalapaka
> Networked Storage Architecture
> Network Storage Solutions Organization
> MS 5668	Hewlett-Packard, Roseville.
> cbm@rose.hp.com
>
> >
> >.
> >.
> >.
> >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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