Incremental messages: micro-kernel services for flexible and efficient management of replicated data

Incremental messages have been designed to efficiently and flexibly manage replicated copies of critical data. We describe this new type of messages and show how applications benefit from an extended message passing interface which provides support for creating updating and recovering data copies, combining the advantages of both kernel and user-level approaches. The paper describes the interface offered to applications, its functionality and how it can be used to implement traditional fault-tolerance mechanisms such as passive replicas, checkpoints and recovery. A fault-tolerant transactional service that exploits the advantages of incremental messages is also presented. Furthermore, the paper presents details about the implementation of incremental messages in VSTa, a micro-kernel based operating system, and the first experimental results obtained.