Performance Study on Supporting Objects in O-Raid Distributed Database Systems

O-Raid [1, 2] uses a layered approach to provide support for objects on top of a distributed relational database system called RAID [3], It reuses the replication controller of RAID to allow replication of simple objects as well as replication of composite objects. In this paper, we first describe the experiments conducted on O-Raid that measure the overheads incurred in supporting objects through a layered implementation, and the overheads involved in replicating objects. The overheads are low (e.g. 4ms for an insert query involving objects). We present experiments that evaluate three replication strategies for composite objects, namely, full replication, selective replication and no replication in a two-site and a four-site O-Raid system. For composite object experiments, the selective replication strategy demonstrated the flexibility of tuning replication of member objects based on the patterns of access. The experimentation is performed in different networking environments (LANs and WANs) to further evaluate the replication schemes. The results indicate that selective replication scheme has greater benefits in WAN than in LAN.