Methods and apparatus for cut-through cache management for a mirrored virtual volume of a virtualized storage system

A method operable in a virtualized storage system, the storage system adapted to couple with a Fibre Channel (FC) initiator and adapted to couple with a plurality of physical FC target devices and adapted to define a virtual FC mirrored volume comprising the plurality of physical FC target devices, the method comprising:

• receiving an FCP_CMD write command from the FC initiator;
• transmitting a multicast FCP_CMD write command to each of the plurality of physical FC target devices responsive to receipt of the FCP_CMD write command;
• receiving an FCP_XRDY from a first physical FC target device of the plurality of physical FC target devices to respond to the multicast FCP_CMD write command;
• transmitting an FCP_XRDY to the FC initiator responsive to receipt of the FCP_XRDY from the first physical FC target device;
• receiving an FCP_DATA including write data from the FC initiator responsive to transmission of the FCP_XRDY;
• storing the write data in a cache memory;
• transmitting an FCP_DATA including the write data to the first physical FC target device as the write data is stored in the cache memory;
• and
• transmitting an FCP_DATA including the write data from the cache memory to each other FC physical target device of the plurality of physical FC target devices.

Apparatus in a virtualized storage system, the storage system adapted to couple with a host system and adapted to couple with a plurality of storage devices, the storage system adapted to define a mirrored virtual volume comprising the plurality of storage devices, the apparatus comprising:

• a host interface adapted to exchange information with an attached host system;
• a back-end interface adapted to exchange information with the plurality of storage devices;
• a cache memory;
• and
• a virtual I/O processor coupled with the host interface and coupled with the back-end interface and coupled with the cache memory, the virtual I/O processor adapted to receive write commands from the host system and adapted to transmit write data associated with a received write command to the cache memory and to the plurality of storage devices, wherein the virtual I/O engine further comprises:
• a cut-through cache processor;
• and
• a forwarding processor,
• the cut-through cache processor adapted to receive a write command and associated write data from the host system and adapted to store the write data in the cache memory and adapted to transmit the write data to a first storage device of the plurality of storage devices as the write data is stored in the cache memory, and
• the forwarding processor adapted to transmit the write data from the cache memory to the other storage devices of the plurality of storage devices.