Image compression and data replication in distributed computing systems

The realization of the need to deal with large-scale systems as a whole and the availability of powerful computer resources have fueled the interest for efficient monitoring and modeling of such systems. This is particularly true in the area of Earth System Science, which has motivated this work. These are projects that need a multicomputer environment. Reasons include requirement for very large computing power, financial constraints that prohibit supercomputers, and fault-tolerance issues. Furthermore, a distributed computing environment is more natural since users and data generation are geographically distributed.; In an Earth System Science computing environment, users should be able to browse the data available, process them, insert new data and correct or enhance data already available. A bottleneck is the handling of image or image-like data--there are a large number of images and the size of each of them is also large.; We propose a scheme that stores images and supports image browsing efficiently. In particular, the scheme achieves good image compression while supporting fast image subregion retrieval at various resolutions. It is particularly suited for a distributed server/client environment.; Since new images are inserted, obsolete ones are deleted and others are updated, support for maintaining data coherence without sacrificing performance is needed. For an image server/client environment to be used as part of a distributed system, which may include other servers that provide related information, all these servers must appear as a single logical entity to any user. We propose an algorithm that achieves such an objective by providing a shared memory abstraction, i.e., access to the memories of the servers appear like accesses to a single memory module. To achieve this efficiently, the algorithm dynamically migrates/replicates/deletes data from/to servers in order to best distribute them to satisfy the current pattern of users' accesses.