Lessons from giant-scale services

Web portals and ISPs such as AOL, Microsoft Network, and Yahoo have grown more than tenfold in the past five years (1996-2001). Despite their scale, growth rates, and rapid evolution of content and features, these sites and other "giant-scale" services like instant messaging and Napster must be always available. Many other major Web sites such as eBay, CNN, and Wal-Mart, have similar availability requirements. The article looks at the basic model for such services, focusing on the key real-world challenges they face (high availability, evolution, and growth), and developing some principles for attacking these problems. Few of the points made in the article are addressed in the literature, and most of the conclusions take the form of principles and approaches rather than absolute quantitative evaluations. This is due partly to the author's focus on high-level design, partly to the newness of the area, and partly to the proprietary nature of some of the information (which represents 15-20 very large sites). Nonetheless, the lessons are easy to understand and apply, and they simplify the design of large systems.