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Abstract:

A number of recent technological trends have made data intensive applications such as continuous media (audio and video) servers a reality. These servers store and retrieve a large volume of data using magnetic disks. Servers consisting of heterogeneous disk drives have become a fact of life for several reasons. First, disks are mechanical devices that might fail. The failed disks are almost always replaced with new models. Second, the current technological trend for these devices is one of annual increase in both performance and storage capacity. Older disk models are discontinued because they cannot compete with the newer ones in the commercial arena. With a heterogeneous disk subsystem, the system should support continuous display while managing resources intelligently in order to maximize their utilization. This study describes a taxonomy of techniques that ensure a continuous display of objects using a heterogeneous disk subsystem. This taxonomy consists of: (a) strategies that partition resources into homogeneous groups of disks and manage each independently, and (b) techniques that treat all disks uniformly, termed non-partitioning techniques. We introduce three non-partitioning techniques: disk merging, disk grouping, and staggered grouping. We investigate these techniques using analytical models. Our results demonstrate that disk merging is the most flexible scheme while providing among the lowest cost per simultaneous display. Finally, using an open simulation model, we compare disk merging with a partitioning technique. The obtained results demonstrate the superiority of disk merging.

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