Cluster Architecture

Introduction

First designed for the Microsoft Windows NT® Server 4.0 operating system, server clusters are substantially enhanced in the Microsoft Windows Server 2003, Enterprise Edition, and Windows Server 2003, Datacenter Edition, operating systems. With server clusters you can connect multiple servers together in order to provide high availability and easy manageability of data and programs running within the cluster. Server clusters provide the following three principal advantages in clustering technology:

• Improved availability by enabling services and applications in the server cluster to continue providing service during hardware or software component failure or during planned maintenance.

• Increased scalability by supporting servers that can be expanded with the addition of multiple processors (up to a maximum of eight processors in Windows Server 2003, Enterprise Edition, and 32 processors in Windows Server 2003, Datacenter Edition), and additional memory (up to a maximum of 8 gigabytes [GB] of random access memory [RAM] in Enterprise Edition and 64 GB in Windows Server 2003 Datacenter Edition).

• Improved manageability by enabling administrators to manage devices and resources within the entire cluster as if they were managing a single computer.

The cluster service is one of two complementary Windows clustering technologies provided as extensions to the base Windows Server 2003 and Windows 2000 operating systems. The other clustering technology, Network Load Balancing (NLB), complements server clusters by supporting highly available and scalable clusters for front-end applications and services such as Internet or intranet sites, Web–based applications, media streaming, and Microsoft Terminal Services.

This white paper focuses solely on the architecture and features of server clusters and describes the terminology, concepts, design goals, key components, and planned future directions. At the end of the paper, the section “For More Information” provides a list of references you can use to learn more about server clusters and the NLB technologies.

Development Background

Computer clusters have been built and used for well over a decade. One of the early architects of clustering technology, G. Pfister, defined a cluster as "a parallel or distributed system that consists of a collection of interconnected whole computers that is utilized as a single, unified computing resource."

The collection of several server computers into a single unified cluster makes it possible to share a computing load without users or administrators needing to know that more than one server is involved. For example, if any resource in the server cluster fails the cluster as a whole can continue to offer service to users by using a resource on one of the other servers in the cluster, regardless of whether the failed component is a hardware or software resource.

In other words, when a resource fails, users connected to the server cluster may experience temporarily degraded performance, but do not completely lose access to the service. As more processing power is needed, administrators can add new resources in a rolling upgrade process. The cluster as a whole remains online and available to users during the process, while the post-upgrade performance of the cluster improves.

User and business requirements for clustering technology shaped the design and development of the cluster service for the Windows Server 2003, Enterprise Edition, and Windows Server, 2003 Datacenter Edition, operating systems. The principal design goal was development of an operating system service that addressed the cluster needs of a broad segment of businesses and organizations, rather than small, specific, market segments.

Microsoft marketing studies showed a large and growing demand for high availability systems in small- and medium-sized businesses as databases and electronic mail became essential to their daily operations. Ease of installation and management were identified as key requirements for organizations of this size. At the same time, Microsoft’s research showed an increasing demand for Windows–based servers in large enterprises with key requirements for high performance and high availability.

The market studies led to the development of the cluster service as an integrated extension to the base Windows NT, Windows 2000, and Windows Server 2003 operating systems. As designed, the service enables joining multiple server and data storage components into a single, easily managed unit, the Server cluster. Server clusters can be used by small and large enterprises to provide highly available and easy-to-manage systems running Windows Server 2003 and Windows 2000–based applications. Server clusters

...