We have developed a video server system for continuous media (cm) data, consisting of a low-priced personal computer (PC) and disk array. The bit rate of the data stream varies depending on which applications are being used, which include video on demand (VOD) and digital video editing systems. Moreover, due to large data volumes, arranging and controlling data with different bit rates on the disk array presents a number of problems. We propose a new file system which utilizes two-layer hierarchical media management: the concept of packages based on the management of contents and disk space, and cm-records based on the management of bit-rate and disk access rate. The size of the packages and the sizes of cm-records are flexible so that a range of bit-rate streams are supported. The site of disk access is decided by taking into account access efficiency, which in turn depends on the continuous media data bit rate. Using these methods it is possible to reduce dramatically the memory space for administration, even for large volumes of data. The file system and the experimental video server have been implemented on a standard PC platform. This prototype system achieved 230.8 Mbps of I/O capability for continuous media.
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