Odysseas I. Pentakalos

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Mass storage systems are finding greater use in scientific computing research environments for retrieving and archiving the large volumes of data generated and manipulated by scientific computations. This paper presents a queuing network model that can be used to carry out capacity planning studies of hierarchical mass storage systems. Measurements taken on(More)
Network attached storage devices improve I/O performance by separating control and data paths and eliminating host intervention during data transfer. Devices are attached to a high speed network for data transfer and to a slower network for control messages. Hierarchical mass storage systems use disks to cache the most recently used files and tapes (robotic(More)
The demands placed on the mass storage systems at various federal agencies and national laboratories are continuously increasing in intensity. This forces system managers to constantly monitor the system, evaluate the demand placed on it, and tune it appropriately using either heuristics based on experience or analytic models. Performance models require an(More)
This paper presents results of preliminary work concerning the analytical modeling of a robotic tape library using stochastic automata. This model is a rst approximation which we use to test the eeciency and accuracy of stochastic automata networks as a modeling tool. The eeects of interactive get and put requests, migration, and purging at online and(More)
1 Abstract| Mass storage systems are nding greater use in scientiic computing research environments for retrieving and archiving the large volumes of data generated and manipulated by scien-tiic computations. This paper presents a queuing network model that can be used to carry out capacity planning studies of the Unitree mass storage system. Measurements(More)
SUMMARY The constant growth on the demands imposed on hierarchical mass storage systems creates a need for frequent reconnguration and upgrading to ensure that the response times and other performance metrics are within the desired service levels. This paper describes the design and operation of two tools, Pythia and Pythia/WK, that assist system managers(More)