An Extended Multimedia Quorum-based Synchronization Protocol

We discuss how to efficiently and consistently manipulate multiple replicas of a multimedia object. Multimedia replicas are characterized in terms of not only data structure but also quality of service (QoS). Multimedia replicas are written in enriching and impoverishing types of write operations where some data is added and removed in a replica, respectively. Computation resources are spent to materialize, i.e. physically update multimedia replicas by encoding and decoding multimedia data. We discuss an extended multimedia quorum-based (EMQB) protocol to reduce the processing overhead of each replica. Here, a replica is not materialized in an impoverishing type of write operation. Even in an enriching type of write operation, only some number, not necessarily all of replicas in a write quorum are materialized. Hence, a newest, materialized replica may not be in a read quorum. Even if one newest replica is surely found in a read quorum, no newest replica might be materialized and a transaction cannot read any replica. In the EMQB protocol, replicas are randomly selected to be in a read quorum until a materialized replica is found. The EMQB protocol is evaluated in terms of the total processing overhead of replicas compared with the quorum-based (QB) protocols. We show that the processing overhead of each replica can be reduced in the EMQB protocol compared with the QB and MQB protocols.