Reducing write I/O latency using asynchronous Fibre Channel exchange

摘要

A FCP initiator sends a FCP write command to a FCP target within a second FC Exchange, and the target sends one or more FC write control IUs to the initiator within a first FC Exchange to request a transfer of data associated with the write command. The first and second FC exchanges are distinct from one another. A payload of each write control IU includes an OX_ID value with which the initiator originated the second Exchange and a RX_ID value assigned by the FCP target for the second exchange. The two Exchanges yield a full-duplex communication environment between the initiator and target that enables the reduction or elimination of latencies incurred in a conventional FCP write I/O operation due to the half-duplex nature of a single FC Exchange. The write control IU may be an enhanced FCP_XFER_RDY IU or a new FC IU previously undefined by the FCP standard.

主权项

1. A Fibre Channel (FC) Protocol for SCSI (FCP) target, comprising:
a FC port; and a processor, adapted to communicate with a FCP initiator via the FC port; wherein the FCP target is configured to send one or more FC write control information units (IUs) to the FCP initiator within a first FC exchange to request a transfer of data associated with a FCP write command IU previously sent to the FCP target by the FCP initiator within a second FC exchange, without the FCP initiator first sending its sequence initiative in the second FC exchange; wherein the first FC exchange is distinct from the second FC exchange; wherein a payload of each of the one or more write control IUs comprises:
an originator exchange identifier (OX_ID) value with which the FCP initiator originated the second FC exchange; anda responder exchange identifier (RX_ID) value assigned by the FCP target for the second FC exchange.