Fibre Channel Storage Array Having Standby Controller With ALUA Standby Mode for Forwarding SCSI Commands

A method for forwarding commands between processes running on a standby controller and an active controller of a storage array, comprising,

• executing a primary process in user space of the active controller, the primary process configured to process request commands from one or more initiators in an active optimized (AO) mode, the primary process having access to a volume manager for serving data input/output (I/O) requests and non-I/O requests;
• executing a secondary process in the user space of the standby controller, the secondary process configured to process request commands from one or more of the initiators in accordance with a standby (SB) mode, the secondary process not having access to the volume manger, the secondary process configured for responding to non-I/O requests;
• receiving a command from an initiator at the standby controller via a port of the standby controller set in the SB mode;
• forwarding the command from the user space of the secondary controller to the user space of the primary controller, the command being forwarded when identified as a command that requires processing by the active controller;
• sending, by the primary process of the active controller, a processed command to the secondary process of the standby controller;
• and
• sending the processed command, by the secondary process of the standby controller to the initiator.

A storage array being a target to initiators communicating over Fibre Channel fabric, comprising,

• an active controller that includes ports that operates in an asymmetric logical unit access (ALUA) active optimized (AO) mode, the active controller includes a first user space that executes a first SCSI layer and a first SCSI forwarding (SFW) module;
• a standby controller that includes ports that operate in an ALUA standby (SB) mode, the standby controller includes a second user space that executes a second SCSI layer and a second SCSI forwarding (SFW) module;
• wherein the second SCSI layer and the second SFW module are configured to identify a type of command that is predefined for forwarding when received via one of the ports operating in the ALUA SB mode;
• wherein the second SCSI layer, the second SFW module, the first SFW module and the first SCSI layer operate to define a SCSI-level nexus connection to enable the forwarding of commands that are predefined for forwarding, the SCSI-level nexus connection configured to avoid transfers back to the Fibre Channel fabric as a result of the forwarding.