SCSI I/O Referral List for Multi-Path Storage Clusters

The patent introduces a referral list as an intermediary mechanism that mediates between the initiator and multiple target devices. The referral list contains port identifiers that redirect I/O requests to appropriate targets, enabling multi-pathing without requiring the initiator to directly manage complex multi-protocol connections. This intermediary structure simplifies the initiator's view while maintaining reliability through multiple access paths.

The SCSI I/O referral mechanism is designed to be universal across multiple transport protocols (FCP, iSCSI, SAS). The same referral list structure and port identifier system work across different protocol types, allowing a single mechanism to provide multi-pathing capabilities universally without requiring protocol-specific implementations, thereby reducing overall system complexity.

The referral list acts as an intermediary that manages redundancy information centrally. By storing multiple port identifiers for the same data in a standardized format, the system achieves data redundancy without requiring each initiator to independently manage redundant connections. The referral mechanism abstracts the complexity of maintaining redundant paths across multiple protocols.

The patent uses parameter changes in the form of port identifiers within the referral list to dynamically redirect I/O requests to redundant data copies. By modifying the port identifier parameters based on which copy is available or preferred, the system manages redundancy efficiently without hardcoding complex redundancy logic, thereby reducing device complexity while maintaining high data redundancy.

The referral list is transmitted in advance before actual data transfer occurs. By providing the initiator with port identifiers for multiple data copies beforehand, the system enables the initiator to efficiently select and access data without requiring complex real-time negotiations. This preliminary provision of routing information improves data transfer efficiency while keeping the overhead limited to the initial referral transmission.

The patent uses a standardized referral list structure that can be copied and reused across multiple I/O operations. Once the referral information with port identifiers is established, it can be referenced repeatedly without retransmitting the entire referral structure, thereby improving subsequent data transfer efficiency while minimizing repeated information overhead. The referral list acts as a reusable template for efficient data access.