Exploiting atomic broadcast in replicated databases.pdfVIP

Exploiting Atomic Broadcast in Replicated Databases Fernando Pedone Rachid Guerraoui Andre Schiper Departement dInformatique Ecole Polytechnique Federale de Lausanne 1015 Lausanne, Switzerland Abstract Database replication protocols have historically been built on top of distributed database systems, and have consequently been designed and implemented using distributed transac- tional mechanisms, such as atomic commitment. We argue in this paper that this approach is not always adequate to eciently support database replication and that more suitable al- ternatives, such as atomic broadcast primitives, should be employed instead. More precisely, we show in this paper that fully replicated database systems, based on the deferred update replication model, have better throughput and response time if implemented with an atomic broadcast termination protocol than if implemented with atomic commitment. 1 Introduction Replication is considered a cheap software based way to increase data availability when compared to hardware based specialised techniques [16]. However, designing a replication scheme that provides reasonable performance and maintains data consistency is still an active area of research both in the database and in the distributed systems communities. In the database context, replication techniques based on the deferred update model have received increasingly attention in the past years [13]. According to the deferred update model, transactions are processed locally at one server (i.e., one replica manager) and, at commit time, are forwarded for certi cation to the other servers (i.e., the other replica managers). Deferred update replication techniques oer many advantages over immediate update techniques, which synchronise every transaction operation across all servers. Among these advantages, one may 1 cite: (a) better performance, by gathering and propagating multiple updates together, and localising the execution at a single, possibly nearby, server (t