What is SCSI “packetization” (also called information units)?
• Answer: Information units is a form of SCSI packetization or encapsulation that is designed to reduce overhead and speed data transfers. The SCSI command and data phases are reduced from a seven to a three phase process and then further combines the status phase and message phase that occur after a data transfer. Also, the timing on the command phase, status phase and message phase is changed from asynchronous to synchronous which results in another reduction in overhead. An “SPI information unit” is a data structure that packetizes data, status, command, task attributes and CRC into various formats. An “information unit transfer” is a transfer of data, status, commands, task attributes, task management, and CRC using only SPI information transfers.
