Abstract
In Primary Backup Replication (PBR) systems, the primary node exclusively performs the task of maintaining object consistency for the whole object store; this causes imbalanced load distribution (i.e., poor resource utilization) and limits scalability. In addition, system's availability and data accessibility are completely lost in case of primary failure. This paper proposes a novel approach that disjoints the exclusive role of the primary node by allowing all nodes (replicas) of the system share the load of maintaining object consistency. We define "object ownership" as the exclusive right of a replica to permit object update. The replica that has this right is called the "owner" of this object. The main idea in the proposed approach is to distribute the ownership of the objects among replicas in the sense that each replica owns the objects that are initially created at it (i.e., created by the clients connected to this replica). Hence, the local object store at each replica can be viewed as if it is logically partitioned into different disjoint sets of objects. Each set is owned by a different replica which controls the update requests of the objects in this set. The proposed Object Ownership Distribution (OOD) approach improves load balancing and resource utilization since all nodes share the load of maintaining object store consistency. Furthermore, it improves scalability since any new replica added to the system will eventually share the load with the existing replicas. In addition, system's availability is improved since an owner failure only renders its own objects unavailable while objects owned by other owners are not affected.