Twintail Peripheral Storage Controller
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
A technique is described whereby performance degradation is eliminated in high availability, fault-tolerant computer systems. A twintail disk controller is used to eliminate redundant system software, with its associated performance degradation, by implementing hardware-mirroring concepts. The twintail controller 10, as shown in the figure, splits the serial processor channel into a primary channel 11 and a mirror channel 12, enabling the primary device 13 and the mirror device 14 to reside on respective channels. When a write input/output (I/O) command is issued to primary device 13, twintail controller 10 flushes the I/O to both the devices 13 and 14. The controller 10 then performs a cycle steal multiplex 15 request to or from the processor at normal processing speeds.