Methods and apparatus for managing asynchronous dependent i/o for a virtual fibre channel target

Apparatus in storage controller of a virtualized storage system, the system comprising a virtual Fibre Channel (FC) target which comprises a plurality of physical FC target devices, the apparatus comprising:

• a virtual I/O processor, coupled with the plurality of physical FC target devices, the virtual I/O processor adapted to receive a host initiated read or write command directed to the virtual FC target and adapted to allocate a range of sequential exchange ID (X_ID) values in response to receipt of the read or write command, the virtual I/O processor further adapted to issue multiple physical I/O operations to the plurality of physical FC target devices where each physical I/O operation includes a corresponding X_ID from the range of sequential X_ID values;
• a primary exchange selection component, coupled with the virtual I/O processor and coupled with the plurality of physical FC target devices, the primary exchange selection component adapted to select a primary X_ID (RX_ID) value based on the X_ID value associated with a first completed physical I/O operation of the multiple physical I/O operations;
• and
• an I/O completion component, coupled with the virtual I/O processor and coupled with the plurality of physical FC target devices, the I/O completion component adapted to determine success or failure of the read or write command based on the completion of the multiple physical I/O operations and further adapted to communicate the success or failure to the virtual I/O processor,
• the virtual I/O processor further adapted to transmit a response to the host system indicating success or failure of the read or write responsive to the communication from the I/O completion component, wherein the response transmitted to the host system utilizes the RX_ID,
• the virtual I/O processor further adapted to release the allocated range of sequential X_ID values responsive to transmitting the response to the host system.

A method operable in virtualized Fibre Channel (FC) storage controller, the controller adapted to couple with one or more host systems and adapted to couple with a plurality of physical FC target devices, the method comprising:

• defining, within the storage controller, a plurality of ranges of exchange identifier (X_ID) values wherein each range comprises a number (N) of sequential X_ID values;
• receiving from a host system a read or write command directed to a virtual FC target, the virtual FC target comprising a portion of each of the plurality of physical FC target devices;
• allocating, responsive to receipt of the command, a selected range from the plurality of ranges;
• issuing multiple physical I/O operations, each physical I/O operation directed to a corresponding one of the plurality of physical FC target devices, wherein each of the multiple physical I/O operations is associated with a corresponding X_ID value of the allocated range;
• communicating with the host system to complete processing of the command wherein the communication with the host system comprises a primary X_ID value selected from the allocated range;
• and
• releasing the allocated range responsive to completing processing of the command.