Summary (An Overview of Windows Clustering Technologies: Server Clusters and Network Load Balancing)
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Cluster technologies are becoming increasingly important to ensure service offerings meet the requirements of the enterprise. Windows 2000 and Windows Server 2003 support three cluster technologies to provide high availability, reliability and scalability. These technologies are: NLB, CLB and Server cluster. These technologies have a specific purpose and are designed to meet different requirements.
Server cluster provides failover support for applications and services that require high availability, scalability and reliability, and is ideally suited for back-end applications and services, such as database servers. Server cluster can use various combinations of active and passive nodes to provide failover support for mission critical applications and services.
NLB provides failover support for IP-based applications and services that require high scalability and availability, and is ideally suited for Web tier and front-end services. NLB clusters can use multiple adapters and different broadcast methods to assist in the load balancing of TCP, UDP and GRE traffic requests.
Component Load Balancing provides dynamic load balancing of middle-tier application components that use COM+ and is ideally suited for application servers. CLB clusters use two clusters. The routing cluster can be configured as a routing list on the front-end Web servers or as separate servers that run Server cluster.
Cluster technologies by themselves are not enough to ensure that high availability goals can be met. Multiple physical locations may be necessary to guard against natural disasters and other events that may cause complete service outage. Effective processes and procedures, in addition to good architecture, are the keys to high availability.