Supporting Dynamic Relocation of Video Data in Disk-Array-Based Video Servers

Although modification operations on multimedia data such as insertion and/or deletion of video clips are rare, they may cause significant degradation of disk I/O performance in disk-array-based video servers. This is because many existing disk-array-based video servers consider only video playback at normal speed and retrieval-oriented VCR-like operations such as fast-forward and rewind without considering relocation of video data. Most conventional video servers provide optimal performance using static placement of video data on multiple disks. In this paper, we propose a method called ‘SRM (Segment Relocation Method)’ which provides uniform loadbalance of disks regardless of the dynamic modification of stored video objects. For modification operations, the segments belonging to the corresponding ‘round’ of disk placement are relocated so that the system guarantees uniform load-balance of multiple disks in all rounds. To justify the significance of the relocation scheme, we evaluate and compare the cost of retrieval in terms of the required buffer size and the number of admitted users.