Design of Scalable Continuous Media Servers with Dynamic Replication

Multimedia applications place high demands for quality-of-service (QoS), performance, and reliability on systems. These stringent requirements make design of cost-effective and scalable systems difficult. Therefore efficient adaptive and dynamic resource management techniques in conjunction with data placement techniques can be of great help in improving performance, scalability and reliability of such systems. In this paper, we first focus on data placement. In the recent past, a great deal of work has focused on "wide" data striping as a way of dealing with load imbalance problems caused by skews in data access patterns. Another approach to dealing with load imbalance problems is replication. The appropriate compromise between the degree of striping and the degree of replication is key to the design of scalable continuous media (CM) servers. In this work we focus on evaluation of this compromise in the context of a hybrid CM server design. Changes in data access patterns lead to other questions: (1) when should the system alter the number of copies of a CM object, and (2) how to accomplish this change. We address (1) through an adaptive threshold-based approach, and we use dynamic replication policies in conjunction with a mathematical model of user behavior to address (2). We do this without any knowledge of data access patterns and with provisions for full use of VCR functionality. Through a performance study, we show that not only does the use of this mathematical model in conjunction with dynamic resource management policies improves the system's performance but that it also facilitates reduced sensitivity to changes in:(a) workload characteristics, (b) skewness of data access patterns, and (c) frequency of changes in data access patterns. We believe that not only is this a desirable property for a CM server, in general, but that furthermore, it suggests the usefulness of these techniques across a wide range of continuous media applications. (Cross-referenced as UMIACS-TR-2001-21

Towards Cost-effective On-demand continuous Media Service: A Peer-to- Peer Approach

To overcome the limited bandwidth of streaming servers, Content Distribution Networks (CDNs) are deployed on the edge of the Internet. A large number of such servers have to be installed to make the whole system scalable, making CDN a very expensive way to distribute media. The primary concern of this research is to find an inexpensive way to alleviate the traffic load for media streaming on the servers in a continuous media service infrastructure. Our approach to solve the above problem is motivated by the emerging concept of peer-to-peer computing. Specifically, we let clients that obtained a media object act as streaming servers for following requests to that media object. Unlike the server/client scheme, peers are heterogeneous in the storage capacity and out-bound bandwidth they can contribute. Secondly, peers are heterogeneous in the duration of their commitment to the community. In our research, we identified the following problems in the context of peer-to-peer streaming: 1) How does the come-and-go behaviors of peers affect the system performance? 2). How do we manage the limited resources contributed by each peer? 3). The design of a peer-to-peer streaming protocol that handles peer failure. Solutions to these problems are described and analyzed. 1

Improved multimedia server I/O subsystems

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.---- Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.The main function of a continuous media server is to concurrently stream data from storage to multiple clients over a network. The resulting streams will congest the host CPU bus, reducing access to the system's main memory, which degrades CPU performance. The purpose of this paper is to investigate ways of improving I/O subsystems of continuous media sewers. Several improved I/O subsystem architectures are presented and their performances evaluated. The proposed architectures use an existing device, namely the Intel i960RP processor. The objective of using an I/O processor is to move the stream and its control from the host processor and the main memory. The ultimate aim is to identify the requirements for an integrated I/O subsystem for a high performance scalable media-on-demand server

Exploiting Traffic Balancing and Multicast Efficiency in Distributed Video-on-Demand Architectures

Distributed Video-on-Demand (DVoD) systems are proposed as a solution to the limited streaming capacity and null scalability of centralized systems. In a previous work, we proposed a fully distributed large-scale VoD architecture, called Double P-Tree, which has shown itself to be a good approach to the design of flexible and scalable DVoD systems. In this paper, we present relevant design aspects related to video mapping and traffic balancing in order to improve Double P-Tree architecture performance. Our simulation results demonstrate that these techniques yield a more efficient system and considerably increase its streaming capacity. The results also show the crucial importance of topology connectivity in improving multicasting performance in DVoD systems. Finally, a comparison among several DVoD architectures was performed using simulation, and the results show that the Double P-Tree architecture incorporating mapping and load balancing policies outperforms similar DVoD architectures.This work was supported by the MCyT-Spain under contract TIC 2001-2592 and partially supported by the Generalitat de Catalunya- Grup de Recerca Consolidat 2001SGR-00218

A Low Cost Two-Tier Architecture Model For High Availability Clusters Application Load Balancing

This article proposes a design and implementation of a low cost two-tier architecture model for high availability cluster combined with load-balancing and shared storage technology to achieve desired scale of three-tier architecture for application load balancing e.g. web servers. The research work proposes a design that physically omits Network File System (NFS) server nodes and implements NFS server functionalities within the cluster nodes, through Red Hat Cluster Suite (RHCS) with High Availability (HA) proxy load balancing technologies. In order to achieve a low-cost implementation in terms of investment in hardware and computing solutions, the proposed architecture will be beneficial. This system intends to provide steady service despite any system components fails due to uncertainly such as network system, storage and applications.Comment: Load balancing, high availability cluster, web server cluster

On the Verge of One Petabyte - the Story Behind the BaBar Database System

The BaBar database has pioneered the use of a commercial ODBMS within the HEP community. The unique object-oriented architecture of Objectivity/DB has made it possible to manage over 700 terabytes of production data generated since May'99, making the BaBar database the world's largest known database. The ongoing development includes new features, addressing the ever-increasing luminosity of the detector as well as other changing physics requirements. Significant efforts are focused on reducing space requirements and operational costs. The paper discusses our experience with developing a large scale database system, emphasizing universal aspects which may be applied to any large scale system, independently of underlying technology used.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 6 pages. PSN MOKT01

Striping Doesn't Scale: How to Achieve Scalability for Continuous Media Servers with Replication

Multimedia applications place high demands for QoS, performance, and reliability on storage servers and communication networks. These, often stringent, requirements make design of cost-effective and scalable continuous media (CM) servers difficult. In particular, the choice of data placement techniques can have a significant effect on the scalability of the CM server and its ability to utilize resources efficiently. In the recent past, a great deal of work has focused on ``wide'' data striping as a technique which ``implicitly'' solves load balancing problems; although, it does suffer from multiple shortcomings. Another approach to dealing with load imbalance problems is replication. The main focus of this paper is a study of scalability characteristics of CM servers as a function of tradeoffs between striping and replication. More specifically, striping is a good approach to load balancing while replication is a good approach to ``isolating'' nodes from being dependent on other system resources. The appropriate compromise between the degree of striping and the degree of replication is key to the design of a scalable CM server. This is the topic of our work. Also cross-referenced as UMIACS-TR-99-4

A schema-based P2P network to enable publish-subscribe for multimedia content in open hypermedia systems

Open Hypermedia Systems (OHS) aim to provide efficient dissemination, adaptation and integration of hyperlinked multimedia resources. Content available in Peer-to-Peer (P2P) networks could add significant value to OHS provided that challenges for efficient discovery and prompt delivery of rich and up-to-date content are successfully addressed. This paper proposes an architecture that enables the operation of OHS over a P2P overlay network of OHS servers based on semantic annotation of (a) peer OHS servers and of (b) multimedia resources that can be obtained through the link services of the OHS. The architecture provides efficient resource discovery. Semantic query-based subscriptions over this P2P network can enable access to up-to-date content, while caching at certain peers enables prompt delivery of multimedia content. Advanced query resolution techniques are employed to match different parts of subscription queries (subqueries). These subscriptions can be shared among different interested peers, thus increasing the efficiency of multimedia content dissemination