A Common Highly Available Windows System Architecture

Windows servers can be used to build a highly available system that hosts a multitier graphical business application. Because the data tier is kept separate from the tier(s) handling business and presentation logic, different high-availability (HA) technologies are appropriate for each tier. In this HA architecture example, a front-end Windows Server 2003 server farm processes business logic and provides the user interface for Web browser clients, while a back-end Windows Server 2003 cluster hosts the data tier on SQL Server. (The back-end data tier could also be hosted on a Windows-based fault-tolerant [FT] server instead of a cluster.)

Client requests are distributed across the front-end servers by using the Windows Network Load Balancing (NLB) service (or by load-balancing hardware such as an F5 BigIP box). The browser clients are stateless, meaning that each transaction can involve a connection to a different front-end server and are not dependent on any particular front-end server.