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Reduced manning in the naval system requires that a given amount of tasks be performed for time-critical and externally paced missions in an accurate and timely manner utilizing less number of personnel in a warship. The MultiModal WatchStation (MMWS) in navy ships provides a mechanism to aid in this endeavor. The focus of this study is on the storage and management of audio clips generated by MMWS operators within and across the navy ships. The generated audio clips must be stored in a persistent storage (i.e., secondary and tertiary storage) in order to facilitate future query on the past messages. Since the persistent storage is distributed across many sites (i.e., ships), a query response time might be intolerable if the requested clips are not stored local to the party submitting the query. In order to improve the query response time, traditional solutions tend to replicate data across all the sites. One problem preventing them from this over- replication is the overhead associated with ensuring data consistency when information is modified. Within the MMWS application, however, the size of audio clips are large and hence it is not cost effective to replicate them at every site. Furthermore, the audio clips once stored are never modified and hence consistency is not an issue. Finally, the types of queries on stored audio clips, and their frequency of submissions are known a priori. This knowledge can be exploited for a selective replication which can improve query response time. Therefore, focusing on MMWS application, we propose a dynamic placement/replacement strategy which intelligently stores read-only and large-size audio clips by considering query workload. We compared the performance of our dynamic strategy with other alternative static strategies using a simulation experiment. Our results indicate that the dynamic strategy is promising with regards to query response time.
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