This was alluded to in one of the Sun performance "bibles" in the section on drive IO ... the book spoke of some "non commodity disks" that had multiple disk ar

This was alluded to in one of the Sun performance "bibles" in the section on drive IO ... the book spoke of some "non commodity disks" that had multiple disk arms that moved independently on different platters. I think it was "Sun Performance and Tuning: Sparc & Solaris" (the Porsche book) but it might have been "Configuration and Capacity Planning for Solaris Servers."