Benefits of an image-oriented parallel file system
Professionals in various fields such as medical imaging, biology, and civil engineering require rapid access to huge amounts of uncompressed pixmap image data. In order to fulfill these requirements, a parallel image server architecture is proposed, based on arrays of intelligent disk nodes, each disk node being composed of one processor and one disk. Pixmap image data is partitioned into rectangular extents, whose size and distribution among disk nodes minimize overall image access times. Disk node processors are responsible for maintaining both the data structure associated with their image file extents and an extent cache offering fast access to recently used data. Disk node processors may also be used for applying image processing operations to locally retrieved image parts. This contribution introduces the concept of an image oriented file system, where the file system is aware of image size, extent size, and extent distribution. Such an image oriented file system provides a natural way of combining parallel disk accesses and processing operations. The performance of the proposed multiprocessor-multidisk architecture is bounded either by communication throughput or by disk access speed. However, when disk accesses are combined with low-level local processing operations such as image size reduction (zooming), close to linear speedup factors can be obtained by increasing the number of intelligent disk nodes.