Supporting partial data accesses to replicated data

Partial data access operations occur frequently in distributed systems. This paper presents new approaches for efficiently supporting partial data access operations to replicated data. We propose the replica modularization (RM) technique which suggests partitioning replicas into modules, which now become the minimum unit of data access. RM is shown to increase the availability of both partial read and write operations and improves performance by reducing access delays and the size of data transfers occurring during operation execution on replicated data. In addition, we develop a new module-based protocol (MB) in which different replication protocols are used to access different sets of replicas, with each replica storing different modules. The instance of MB we discuss here is a hybrid of the ROWA (Read One Write All) protocol and the MQ (Majority Quorum) protocol. MB allows a trade-off between storage costs and availability. We show that MB can achieve almost as high availability as the MQ protocol, but with considerably smaller storage costs