Link analysis and design of high speed storage buses in backplane and cabling environments

This paper discusses electrical performance and design aspects of SAS (Serial Attached SCSI) link channels in various server storage system configurations through modeling and simulation analysis in frequency and time domain. The signal loss behaviors are investigated in two interconnect structures, internal SAS links in host enclosure backplanes and external SAS links in cabling environment. While signals in external SAS links experience excessive loss through lengthy cables in meters, those of internal SAS links are impaired by multiple discontinuities of board components over less than a couple of feet of PCB routing though largely dependent of system design. While eye closure is parallel to loss magnitude in general, higher degree of discontinuities exhibited in frequency loss behavior of channels result in more eye closure despite lower loss magnitude reducing design space budget and the impact is greater with higher data rates.