On the trade-offs between the file redundancy and the communication costs in distributed database systems

The operating cost of distributed database systems (DDBS) usually depends on the storage costs of file copies, i.e file redundancy, and the communication cost of queries and for updates. A basic model is proposed to clarify the tradeoffs between the file redundancies and the communication cost of queries from the viewpoint of rate-distortion theory and its applications, for the case in which almost all requests are assumed to be queries. The result suggests that the addition of a few file copies is effective for the bus or ring network subsystems and the existence of only one file is essential to the star network subsystem, as the system size becomes large. The model leads to a useful measure for selecting the file-allocation design of a large scale DDBS