Structure and process for distributing SCSI LUN semantics across parallel distributed components

摘要

Briefly, the present invention provides a system and method for distributing SCSI semantics throughout a network. Specifically, the present invention distributes the SCSI semantics through multiple parallel agents and a separate controller. This configuration allows performance-sensitive distribution of SCSI semantics to be parallelized and optimized for performance in the agents, while the control and management of the SCSI semantics is centralized in the controller chosen for optimal cost, management, and other implementation practicalities. In this design, the SCSI semantics are stored in the controller, and portions of the SCSI semantics are distributed to the mapping agents as cached, read-only information. The controller is responsible for persistent storage of the SCSI semantics, thereby consolidating the costs and management for the SCSI semantics in a single component. The agents preferably do not interact with other mapping agents, thereby improving the scalability of virtual storage systems and their tolerance of component failures. Within an embodiment of the SCSI distribution system, key SCSI semantic information is distributed to the agents while infrequently used semantic information is centralized in the controller. Likewise, SCSI commands that cannot be processed by the agents may be forwarded to the controller.