Performance Estimates for Low Fat Protocol 1 To: Improved Scsi Protocol Ad-hoc Group From: Andrew Wilson ([email protected]) Subject: Performance Estimates for Low Fat Protocol Date: Monday

As the synchronous data transfer portion of a SCSI request becomes faster and faster, the time spent in SCSI protocol overhead becomes an ever increasing fraction of the total time. While substantial reductions in overhead can still be obtained by improving SCSI device implementations, there is a lower limit built into the SCSI protocol which will restrict performance at Fast-80 speeds. In response to this, Adaptec is proposing a set of protocol enhancements, collectively referred to as the Low Fat Protocol (LFP) which seek to further reduce the minimum SCSI protocol overhead, thus allowing efficient utilization of the Fast-80 SCSI bus. This white paper will demonstrate the benefits that can be obtained from these protocol enhancements and show how their inclusion results in reasonable SCSI efficiency, even for smaller transfer lengths.