Re: iSCSI:Clear Task Set

["Mallikarjun C." <cbm@rose.hp.com>]

Julian,

I tend to agree with John on this one. 

Passing the 'clear task set' onto target SCSI layer once
the current session is dealt with is the right choice.  That
avoids iSCSI having to say anything on the relative order 
across sessions, and also addresses the issue John raised -
that of differing LUN mappings for the same LU.

At a minimum, the second sentence in the current wording  

"All tasks associated with the specified LUN and initiator. 
 For all other initiators all tasks at LUN with no regard 
 to order."

should be dropped since it implies that 'clear task set' affects 
all other initiators.  In fact, this determination can not be made 
until the TST bit is checked in the SCSI control mode page - which 
is completely in the SCSI realm.  That of course requires the task 
management function to be propagated up.

Regards.
-- 
Mallikarjun 


Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668 Hewlett-Packard, Roseville.
cbm@rose.hp.com

Julian Satran wrote:
> 
> John,
> 
> That looks more like in  T10 territory.
> T10 defines differently Abort Task Set and Clear Task Set.
> We could either:
> 
> decide not to implement clear task set (T10 allows that but "per target"
> not "per transport")
> enable clear task set - in which case we have to say something about the
> relative order of the task management request with regard to the  task
> comming from other initiators - and that is what I attempted to say in 9.4
> 
> Julo
> 
> John Hufferd/San Jose/IBM@IBMUS
> Sent by: owner-ips@ece.cmu.edu
> 23-11-01 23:30
> 
> 
>         To:     Julian Satran/Haifa/IBM@IBMIL
>         cc:     ips@ece.cmu.edu
>         Subject:        Re: iSCSI:Clear Task Set
> 
> 
> 
> Julian, and list,
> The question now becomes, if we have all that carefully thought out
> processing that is defined in 9.4 in how to handle the other
> Tasks/Commands
> that are "In Flight", and not yet given to SCSI, how does that apply to
> the
> other Sessions with other initiators?
> 
> That is, at the iSCSI Target layer we do not have the LU Number to LU
> mapping on any Session with any Initiator, so how do we cause the careful
> processing, which is defined in 9.4, to occur on the other sessions that
> may have and association to the subject LU? Especially since all we know
> is
> a LU Number on the Clearing Session.
> 
> Perhaps we do not care about the 9.4 processing on the other Session and
> Other Initiators and just let SCSI layer do its thing, and at the iSCSI
> layer we pay no attention to the other Sessions.  Do you think this is
> correct?
> 
> .
> .
> .
> 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
> 
> Julian Satran/Haifa/IBM@IBMIL@ece.cmu.edu on 11/23/2001 07:56:36 AM
> 
> Sent by:  owner-ips@ece.cmu.edu
> 
> To:   ips@ece.cmu.edu
> cc:
> Subject:  Re: iSCSI:Clear Task Set
> 
> John,
> 
> The LUN is just a mistake there - in all three instances it should be LU.
> The definitions are in accordance with SAM . There are two task management
> modes - tasks sets-per-initiator at each LU or common for all initiators.
> The mode is a SCSI issue controlled by a field in the Control-Mode page.
> Clear task set MAY clear all the tasks in the task set - even if common to
> all initiators if that is the way the task set is managed. That is also
> the difference between clear-task-set and abort task set.
> 
> Julo
> 
> John Hufferd@IBMUS
> 23-11-01 11:29
> 
>         To:     Julian Satran/Haifa/IBM@IBMIL@IBMDE
>         cc:     ips@ece.cmu.edu
>         From:   John Hufferd/San Jose/IBM@IBMUS
>         Subject:        iSCSI:Clear Task Set
> 
> Julian, and List  (using v 0.9)
> In point 9.4, just before 9.5  the Table entry associated with Clear Task
> Set applies to:
> 
> "All tasks associated with the specified LUN and initiator. For all other
> initiators all tasks at LUN with no regard to order."
> 
> Perhaps we mean LU here, but I know that the iSCSI layer does not have
> information about LU, only about the LU Number (LUN) in the command.  We
> can not tell, at the iSCSI layer, if the  LU represented  by a LUN on
> Session 1, has any relationship to any LUN on any other session.
> 
> This is because each initiator may have their own numbering for LUs.
> Therefore, do we just pass the Clear Task Set to the SCSI layer and hope
> for the best, or does the iSCSI layer also suppose to apply the Clear Task
> Set to all the sessions that it has coming into the iSCSI (SCSI) Target
> Port?  If the latter, again how will that work when the iSCSI layer has no
> idea what LU an Initiator's LUN will map to?
> .
> .
> .
> 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