Martin G. Kienzle

A dynamic policy of segment replication for load-balancing in video-on-demand servers

In a video-on-demand server, resource reservation is needed for continuous delivery. Hence, any given server can serve only a fixed maximum of clients. Different videos can be placed on different disks or disk array groups. Since the access rates to various movies are not uniform, load imbalance can occur among the disks in the system. In this paper, we propose a dynamic policy that replicates segments of files to balance the load across the disks. By using simulation, we show that the proposed policy is responsive to quick load surges and is superior to a policy based on the static replication of hot movies.

Using tertiary storage in video-on-demand servers

Video-on-demand is a new entertainment service that will soon be widely available. A small amount of material is very popular, while large amounts of material are viewed less frequently. This skew can be exploited by using a storage hierarchy, storing the less frequently viewed videos in lower-cost tertiary storage. This paper studies the use of tertiary storage for videos. Tertiary storage devices such as optical disks and magnetic tapes can be used to a) deliver data directly to viewers, or b) to stage data to disk for viewing. Analysis of these modes yields guidelines for server design. Examining device characteristics, workload characteristics, and cost, the two modes are compared to each other and to playing from disk. The data placement decision depends on the fraction of time a stream of a video is active. At current costs, videos having an active stream less than a third of the time should reside on tertiary storage. When a tertiary library has a much higher data rate than the video rate, videos should be staged disk for playing. Otherwise, they should be played directly from tertiary store.

A methodology for evaluating storage systems in distributed and hierarchical video servers

Large scale multimedia systems combine technologies from audio and video systems, communications systems and computer systems. Multimedia systems store compressed video files digitally on a server that is shared by a large number of users. A video server is characterized by the number of simultaneous video streams it can support and by the size of the video library. Storage costs are a significant aspect of a video server because of the very large size of the objects. In setting up a video service, there is a choice between having one very large central server, multiple decentralized servers, or a hierarchical server structure. This paper discusses the scaling and cost issues in the server in order to provide information on how to balance server costs against communications costs.<<ETX>>

e-Seminar lecture recording and distribution system

e-Seminar is an IBM-Research internal prototype platform to allow all IBM-Research employees access to videos and slides of talks, seminars, presentations and other events at any IBM- Research campus worldwide. The platform facilitates an increased use of digital video by lowering the cost and complexity thresholds for the use of video in live and in on demand applications. The e-Seminar system therefore increases the leverage of intellectual property, and helps to improve the communication between the laboratories of the IBM-Research Division. All of the above is reached through use of a distributed Video-on-Demand system on all sites of the IBM- Research Division. It is a highly integrative project, assembling tools, techniques and insights from a broad variety of knowledge fields including but not limited to networking, video recording/encoding, data streaming, video analysis, HCI, MM authoring, data visualizing and distributed systems management. The e-Seminar system is designed to serve as a base platform to perform research on the broad range of all these areas. Currently ongoing research in the project explores how such a system can be built and operated with the least amount of people involved while at the same time reducing the breadth and depth of skills necessary. Additional research is done in the area of real time analysis and indexing of the given material in ways that are relevant to the teaching purpose of the system. Also new ways of video network caching are explored.

A performance model of a connection-oriented hypercube interconnection system

Abstract Connection-oriented communication is becoming more and more important in the very high-speed (Gbps) communication environment. Under connection-oriented communication, all communication resources at the source (buffers, connection points), in the network (trunks), and at the destination (buffers, processing capacity) must be available before the start of a transmission. This paper presents an analytic model of a direct hypercube interconnection system operating in connection-oriented mode. Due to the high complexity of an exact model of such a system, a tractable approximate model is developed that exploits the systems symmetry to obtain a concise state description. We use our model to evaluate the performance of hypercube interconnection systems. We find that the contention for trunks is small compared to the contention for destination resources. A strategy of checking the resource availability of all waiting connection requests whenever a connection terminates, combined with random path selection, is shown to result in good load/delay characteristics. We further find that the system treats connections of all lengths equally. That is, counterintuitively, connections with shorter paths are not favored over connections with longer paths. We can thus conclude that in addition to good throughput/delay performance, random path selection is fair, and no other measures need be taken to ensure fairness.

An HIPPI interconnection system

The proposed HIPPI standard, a connection-oriented communication standard for very-high-speed interconnection systems connecting high-end computing systems, is discussed. The problems of managing connections and of configuring the interconnection system as either a single crossbar switch or as a clique of crossbar switches are considered. Three connection management policies are introduced: a centralized policy, a broadcast policy, and a distributed policy. To compare these policies for different system configurations, a set of models is introduced and used to evaluate a range of interconnection system configurations. The results of these models and the use of a cost measure make it possible to compare the cost and performance of different configurations and alternative connection management policies. >

Challenges of business media

The full integration of digital media as a commonly available data type for business applications causes a major transition in computing infrastructure and solution architectures. While many corporate uses of digital media can be handled with the current infrastructure, as the amount and file size of the digital media grows, more than simple capacity improvements need to be implemented. The business needs for media are concrete; the problems we need to address are real. Our community needs to find real solutions too, for high-level semantic analysis, provisioning and management of mixed-media information, and distribution and delivery of media data to satisfy requirements dictated by business scenarios. The paper describe a few scenarios that show how corporations are using digital media to enhance their employee and customer communications, improve the effectiveness and efficiency of business processes, and create new business and revenue opportunities.

Effect of video server topology on contingency capacity requirements

Video servers need to assign a fixed set of resources to each video stream in order to guarantee on-time delivery of the video data. If a server has insufficient resources to guarantee the delivery, it must reject the stream request rather than slowing down all existing streams. Large scale video servers are being built as clusters of smaller components, so as to be economical, scalable, and highly available. This paper uses a blocking model developed for telephone systems to evaluate video server cluster topologies. The goal is to achieve high utilization of the components and low per-stream cost combined with low blocking probability and high user satisfaction. The analysis shows substantial economies of scale achieved by larger server images. Simple distributed server architectures can result in partitioning of resources with low achievable resource utilization. By comparing achievable resource utilization of partitioned and monolithic servers, we quantify the cost of partitioning. Next, we present an architecture for a distributed server system that avoids resource partitioning and results in highly efficient server clusters. Finally, we show how, in these server clusters, further optimizations can be achieved through caching and batching of video streams.

Multimedia file serving with the OS/390 LAN server

The rapidly increasing storage and transmission capacities of computers and the progress in compression algorithms make it possible to build multimedia applications that include audio and video. Such applications range from educational and training videos, delivered to desktops in schools and enterprises, to entertainment services at home. Applications developed for stand-alone personal computers can be deployed in distributed systems without change by using the client/server model and file servers that allow the sharing of applications among many users. The OS/390™ LAN Server has been enhanced to support multimedia data delivery. Resource management and admission control, wide disk striping to provide high data bandwidths, and multimedia-specific performance enhancements have been added. The resulting server benefits from the robustness, scalability, and flexibility of the S/390® system environment, which allows it to move into new multimedia applications. Multimedia support on a robust, widely installed platform with little or no additional hardware requirements gives customers the opportunity to enhance their existing applications with multimedia features and then expand their capacity as the demands of the applications increase. This multimedia server platform is in use with several interesting applications.

Distributed stream control for self-managing media processing graphs

Interactive media applications have moved the ability to manipulate content as it is being streamed from a desirable feature to a required attribute for video servers. However, present day video server architectures continue to focus primarily on disk and network strategies for maximizing the number of concurrent streams while adhering to Quality of Service (QoS) requirements, If video servers are to manage large numbers of disparate streams exploiting a wide variety of processing algorithms, server architectures must be extended to support the integration of arbitrary isochronous processing algorithms. We believe server support for these stream processing graphs present new research challenges in video server buffer management, distributed stream control and QoS management. In this paper, we propose distributed stream control techniques which form a foundation for developing technology to address these new challenges. We have implemented the recommended techniques in the context of a commercial video server.