Enhancing Patching Performance Through Double Patching

Patching is an efficient bandwidth-sharing technique for video-on-demand systems. Its performance, however, has limitation: as the time distance to the last regular multicast enlarges, the patching cost for new requests increases and eventually, a new regular multicast must be scheduled to balance the cost. In this paper, we address this problem by proposing a new technique called Double Patching. Our research is based on the observation that a patching stream can be shared by the video requests arriving in the next wp time units if it delivers an additional 2 ·wp time units of video data. With these additional data, the patching cost for these requests can be significantly reduced. Our performance study shows that the new technique can dramatically improve, in many workloads double, the performance of the original Patching. While the performance gain is significant, the new technique inherits the same simplicity from the original Patching. In particular, it does not impose any additional requirement on client download bandwidth the same as the original Patching, the new scheme allows a client to receive data from no more than two video streams at any one time.