In direct comparison with a 2.5" notebook hard drive, the Savvio is much higher at 15 mm. Although these sort of "fat" drives have been around for notebooks, they have died out in the last few years.
The Savvio is at the top of the picture - that thing resembling a smartphone. The SCSI interface also needs elbowroom - the SAS version will be smaller still.
Greater integration means the boards can be downsized to 2.5" format. 8 MB Cache (SDRAM) are on tap - up to 32 MB is child's play.