Virtually all Web-centric data centers follow the three-tier model: Web sever tier, application server tier, and database server tier. While the specific topology in which these tiers are configured depends on the service provided, the fundamental infrastructure components are common across deployments. The method of load balancing traffic to the sites, the means of replicating data throughout the site, and even the physical layout of the servers are all issues to consider in data center design.

This collection of articles touches on the infrastructure components, providing an overview of the typical data center and setting the foundation for intelligent tradeoffs when analyzing a Web site?s specific scaling and application needs.

The first article, "Architecture and Dependability of Large-Scale Internet Services," provides an excellent overview of popular Web site data centers, and characterizes several distinct deployment models. Not only are the key components of the data center highlighted, but the reasoning behind the configuration choices is explained. The next article, "Lessons from Giant-Scale Services," goes into detail about the actual vendor and design options, focusing more on the load balancing aspects than the database aspect. Although the article is slightly dated in terms of the actual vendor offerings (it seems that vendors are coming out with newer models every year, or every other year), the concepts remain relevant in today?s data center architectures.

Focusing slightly more on the database tier, "Data Management Issues in Supporting Large-Scale Web Services," provides a first-hand look at some of the design decision and data center components involved in storing and replicating data for a major Internet application (Hotmail).

Rounding out this collection, "Power and Energy Management for Server Systems," analyzes the power consumption of both Web and database servers, describing the various usage levels depending on the type of work they are doing. Although this aspect of data center design is less technical, it remains an important aspect when focusing on green technology, as well as the minimizing of operational costs.

With this collection, readers will walk away with an idea of the core infrastructure involved in Web site data centers design.

Wes Chou is an engineering manager in Cisco's Application Delivery Business Unit. He has experience with large-scale application-aware networks and has seen load balancers placed in every possible location imaginable within a network. He serves on the Editorial Board of IT Professional.