A disk shaped cassette for centrifugal fluid separation, particularly blood separation, and a drive system for high speed rotation of the cassette. The cassette is driven at speeds which permit very rapid separation of the blood in times on the order of seven (7) to twenty (20) seconds by an automated control. The cassette is supported by a flexible support coupling and mounting system that permits the entire rotating mass to spin about the center of mass unique to the particular cassette as filled. The cassette typically includes a peripheral collection chamber which may be either annular, lobed or channel shaped. A cassette enabled to hold plural separation tubes is also shown. A gel can be placed in the cassette with a density between the fluid components to be separated and after centrifuging maintains the component separation that centrifuging creates. Because the cassette disperses the fluid components, markings may be molded into the cassette or placed against it to permit volumetric gauging of the centrifuged components. The cassette is provided in various configurations to provide control over the exchange of fluid between collection chambers and to facilitate the separation functions.