Towards an Integrated Approach to Fault Tolerance in Delta-4

As part of the European Strategic Programme for Research in Information Technology (ESPRIT), the Delta-4 project is seeking to define an open, fault-tolerant, distributed computing architecture. The Delta-4 approach to fault-tolerance is based upon the replication of software components on distinct host computers. It deals primarily with hardware fault tolerance (i.e. the tolerance of the system to hardware failures), but also addresses other areas of dependability, including software fault tolerance. This paper describes the architecture of the Delta-4 project and considers methods of achieving tolerance to software design failures in addition to hardware failures. The incorporation of these methods into the overall Delta-4 architecture are also described.