iSCSI : Section 2.4.2. Error Communication Latencies.

[Santosh Rao <santoshr@cup.hp.com>]

All,

The rev 05 draft mandates targets to wait until all the Data PDUs of an
exchange have been received, prior to communicating any error with the
I/O that may have occurred on an earlier I/O. Why is this needed ? This
only adds additional latency to error communication from target to
initiator and can cause large delays in communicating an error with long
lasting I/Os like tape.

The ability to communicate an error on its occurrence is something other
SCSI transports provide and it requires the target to be capable of
safeguarding against the arrival of stale frames of a PDU from an old
exchange, something which should be possible and required in any case.

Regards,
Santosh

 Section 2.4.2, pg 36
---------------
"If a SCSI device error is detected while data from the initiator is
still expected (the command PDU did not contain all the data and the
target has not received a Data PDU with the final bit Set) the target
MUST wait until it receives the a Data PDU with the F bit set before
sending the Response PDU."



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