We present network flow buffering, which is the use of a remote flow-regulating buffer that is deployed between a Web client and server to improve performance of HTTP-based playback of video. We show that HTTP enhanced with network flow buffering significantly improves performance, especially under high packet loss and highly variable bandwidth conditions, when compared with using either straight HTTP or streaming. The benefits of network flow buffering are numerous, and include reducing interruptions to playback, maintaining high video-image quality, and decreasing client-buffering requirements. Network flow buffering is easily implemented with existing Web mechanisms.

We present a new Web middleware architecture that allows users to customize their view of the Web for optimal interaction and system operation when using non-traditional resource-limited client machines such as wireless PDAs (personal digital assistants). Web Stream Customizers (WSC) are dynamically deployable software modules and can be strategically located between client and server to achieve improvements in performance, reliability, or security. An important design feature is that Customizers provide two points of control in the communication path between client and server, supporting adaptive system-based and content-based customization. Our architecture exploits HTTP's proxy capabilities, allowing Customizers to be seamlessly integrated with the basic Web transaction model. We describe the WSC architecture and implementation, and illustrate its use with three non-trivial, adaptive Customizer applications that we have built. We show that the overhead in our implementation is small and tolerable, and is outweighed by the benefits that Customizers provide.

Declustered data organizations in disk arrays (RAIDs) achieve less-intrusive reconstruction of data after a disk failure. We present PDDL, a new data layout for declustered disk arrays. PDDL layouts exist for a large variety of disk array configurations with a distributed spare disk. PDDL declustered disk arrays have excellent run-time performance under light and heavy workloads. PDDL maximizes access parallelism in the most critical circumstances, namely during reconstruction of data on the spare disk. PDDL occurs minimum address translation overhead compared to all other proposed declustering layouts.