Constant time permutation: an efficient block allocation strategy for variable-bit-rate continuous media data

To provide high;accessibility of continuous-media (CM) data, CM servers gen erally stripe data across multiple disks. Currently, the most widely used s triping scheme for CM data is round-robin permutation (RRP). Unfortunately, when RRP is applied to variable-bit:rate (VBR) CM data, load imbalance acr oss multiple disks occurs, thereby reducing overall system performance. In this paper, the performance of a VER CM server with RRP is analyzed. In add ition,we propose an efficient striping scheme called constant time permutat ion (CTP),which takes the VER characteristic into account and obtains a mor e balanced load than RRP. Analytic models of both RRP and CTP are presented , and the models are verified via trace-driven simulations. Analysis and si mulation results show that CTP can substantially increase the number of cli ents supported, though it might introduce a few seconds/minutes of initial delay.