Re: iSCSI: DataRN

[julian_satran@il.ibm.com]

Santosh,

The ACK for a response is when status is ACKed (by the status numbering).

Before this ack a target has several options for restart:

   to keep all the data (recall we have dropped DataRN) and "restart
   sending".
   not to keep data and reject the command restart with a service response
   (that we have to specify) of restart reject (your tape target may want
   to do just this)
Alternatively we may want in the restart to indicate the phase the command
was in (Data Transfer or Status) and to let the target react accordingly
but I am not sure it is worth the effort.

Regards,
Julo

Santosh Rao <santoshr@cup.hp.com> on 23/01/2001 20:56:34

Please respond to Santosh Rao <santoshr@cup.hp.com>

To:   Julian Satran/Haifa/IBM@IBMIL
cc:   ips@ece.cmu.edu
Subject:  Re: iSCSI: DataRN




julian_satran@il.ibm.com wrote:

>
> The above is correct if the digest error or connection failure occurred
on
> delivery of the command. If a digest error were to be detected by an
> initiator on the response PDU (by which time the target has already
> completed the operation and the TCP layer at the initiator has already
> sent the ACK), then, the command is complete from the device perspective
> and should not be retried.
>
> <js> how would that happen ? </js>

Julian,

If the initiator detected a digest error on the Response PDU[and the target
has completed all or part of the data phase], such an operation cannot be
retried without a prior rewind command, in the case of sequential media.

The iSCSI layer cannot retry commands destined to sequential media when
there
is a possibility that some or all of the data phase is complete.

Regards,
Santosh

 - santoshr.vcf