Abstract: A system for enabling SATA drives to be utilized in FC SANs is disclosed. To send data to a SATA drive over a FC SAN, a host sends SCSI commands encapsulated in FC frames over a standard FC link to a Fibre Channel Attached SATA Tunneling (FAST) RAID controller, where the SCSI commands are de-encapsulated from the FC frames and translated to SATA FISs. The SATA FISs are thereafter encapsulated into FC frames. The IOC that performs these functions is referred to as a FAST IOC. The SATA-encapsulated FC frames are sent to multiple disk drive enclosures over another standard FC link. The FC frames are de-encapsulated by FAST switches in disk drive enclosures to retrieve the SATA FISs, and the SATA FISs are sent to the SATA drives over a SATA connection.

Abstract: A prerequisite-based scheduler is disclosed which takes into account system resource prerequisites for execution. Tasks are only scheduled when they can successfully run to completion and therefore a task, once dispatched, is guaranteed not to become blocked. In a prerequisite table, tasks are identified horizontally, and resources needed for the tasks are identified vertically. At the bottom of the table is the system state, which represents the current state of all resources in the system. If a Boolean AND operation is applied to the task prerequisite row and the system state, and if the result is the same as the prerequisite row, then the task is dispatchable. In one embodiment of the present invention, the prerequisite based scheduler (dispatcher) walks through the prerequisite table from top to bottom until a task is found whose prerequisites are satisfied by the system state. Once found, this task is dispatched.