The online auction site ebay is very popular indeed it is so popular that its web servers deliver hundreds of millions of pages per day these pages are a combination of static html pages and dynamically generated wed pages the dynamic pages are created from queries run against ebay's oracle database in which it keeps all of the information about all auctions that are under way or have closed within the most recent 30 days with millions of auctions under way at any moment this database is extremely large the combination of a large database and high-transaction volume makes ebay's web server operation an important part of the company's success and a potential contributor to its failure the servers at ebay failed more than 15 times during the first five years (1995-2000) of the company's life the worst series of failures occurred during may and june of 2000 when the site went down four times one of failures kept the site offline for more than a day-a failure that cost ebay an estimated 5 million the company's stock fell 20 percent in the days following that failure at that point ebay's decided it needed to make major changes in its approach to web server configuration many of ebay's original technology staff had backgrounds at oracle a company that has a tradition of selling large databases that run on equally large servers further the nature of ebay's business-any visitor might want to view information about any auction at any time-led ebay management initially to implement a centralized architecture with one large database residing on a few large database server computers lt also made sense to use similar hardware to serve the web pages generated from that database in mid-2000 following the worst site failure in its history ebay decided to move to a decentralized architeeture this was a tremendous challenge because it meant that the sinhle large auction information database had to be replicated across groups or clusters of web and database servers however ebay realized that using just a few large servers had made it too vulnerable to the failure of those machines once ebay completed the move to becentralization it found that adding more capacity was easier instead of installing and configuring a large server that might have represented 15 percent or more of the site's total capacity clusters of six or seven smaller machines could be added that represnted less than one percent of the site's capcity routine periodic maintenance on the servers also becam easier to schedule the lesson from ebay's wed server troubles is that the architecture should be carefully chosen to meet the needs of the site web server architecture choices can have a significant effect on the stability reliability and ultimately the profitability fo an electronic commerce wed site.