Re: rationale to send PDUs in increasing CmdSn on single connection

["Eddy Quicksall" <Quicksall_iSCSI@xxxxxxxxxxxxx>]

With my target, if I receive CmdSN's out of order I will re-order them 
before they proceed to the SCSI layer. Since this is necessary for 
multi-connections then it just falls out for single connections.

Also, don't forget that if the Queue Algorithm Modifier is 1 (which it 
usually is) then simple commands can execute in any order regardless of the 
CmdSN (i.e. once it reaches the SCSI layer). So just give the increasing 
CmdSN and the target will, on a single connection, immediately forward the 
command to the SCSI layer and then the optimizations you are thinking of 
will most likely take place.

Eddy

----- Original Message ----- 
From: "Parav Pandit" <paravpandit@xxxxxxxxx>
To: "Paul Koning" <pkoning@xxxxxxxxxxxxxx>
Cc: <David_Sheehy@xxxxxxxxxxxxxx>; <ips@xxxxxxxx>; 
<Julian_Satran@xxxxxxxxxx>
Sent: Wednesday, September 05, 2007 9:00 AM
Subject: RE:  rationale to send PDUs in increasing CmdSn on single 
connection


> --- Paul Koning <pkoning@xxxxxxxxxxxxxx> wrote:
>
> > >>>>> "Parav" == Parav Pandit
> > <paravpandit@xxxxxxxxx> writes:
> >
> >  Parav> If I take pragmatic approach, Any idea,
> > currently how current
> >  Parav> single connection target implementation is?
> >
> > I suspect most of them are single connection.
>
> >  Parav> I mean, if current targets are smart enough
> > (accept out of
> >  Parav> order PDUs on single connection- liberal on
> > point 3.2.2.1),
> >  Parav> then initiators can use their DMA
> > optimization.  What do you
> >  Parav> say?
> >
> > Don't.
> >
> > You'd be creating an initiator that violates the
> > protocol spec.  You'd
> > have no reason to expect that to work at all.  Many
> > targets will check
> > this and call it a protocol violation (you may end
> > up with the
> > connection terminated).  Some may not notice but may
> > end up doing the
> > wrong thing.
> >
> >       paul
>
> [Parav] Thanks Paul. I certainly don't want to violate
> the protocol. I was wondering how current qualified,
> proven iscsi targets are behaving for this scenario.
> And you confirmed the same, so will surely adhere to
> the protocol.
>
> Thanks,
> Parav
>
>
>
>
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