I think piru is referring to
this.
But for the SATA vs SCSI question.
performance gain itself is not enough to defend the costs of SCSI. But security makes it a whole other matter.
Though. running RAID 5/6 on SATA would be more economic and on a workstation you would never tell the difference.
Large servers would probably benefit of SCSI...
but SATA is a very good competitor.
Especially considering the fact that SATA and SAS- SCSI uses almost the same interface. (SATA II drives can be used in SAS backplanes)