Capacity planning an essential tool for managing Web services

V.A.F. Almeida, D.A. Menasce
2002 IT Professional Magazine  
Speed, around-the-clock availability, and security are the most common indicators of quality of service on the Internet. Management faces a twofold challenge. One the one hand, it has to meet customer expectations in terms of quality of service. On the other hand, companies have to keep IT costs under control to stay competitive. Therefore, capacity, reliability, availability, scalability, and security are key issues to Web service managers. Electronic business sites are complex computer-system
more » ... architectures, with multiple interconnected layers composed of many software and hardware components, such as networks, caching proxies, routers, load balancers, high speed links, and mainframes with large databases. The nature of electronic business workload is also complex due to its transactional nature, security and authentication requirements, payment protocols, and the unpredictable characteristics of service requests over the Internet. Planning the capacity of electronic business services requires more than just adding extra hardware. It requires more than intuition, ad-hoc procedures, or rules of thumb. Many possible alternative architectures can be used to implement a Web service; one has to be able to determine the most cost-effective architecture and system. This is where the quantitative approach and capacity planning techniques come into play. Capacity planning techniques offer much more than just performance prediction. In these times of ubiquitous Internet services and businesses, capacity planning should be actually viewed as a powerful management technique. Performance problems on the Internet are exacerbated by the unpredictable nature of service requesting and information retrieval over the Web. It is not uncommon for Web sites to experience, without warning, a manifold increase in traffic volume. This type of load spike, also known as "flash crowds," creates terrible performance problems and slow page download times. Web delays frustate customers and cost over four billion dollars each year to online businesses according to an Intelliquest report (www.intelliquest.com/press/). The causes of delays are various. Overloaded networks and servers are the most common ones. The viability of electronic business depends on the ability of the IT infrastructure to offer timely and reliable services. For companies, whose business depends on the behavior of their online services, long waiting times and unavailability can be disastrous. Electronic businesses must continuously guarantee quality of service to avoid losing sales and customers. Security, performance, and availability are key issues for any service on the Web. This article introduces capacity planning as an essential tool for managing quality of service on the Web and presents a methodology, where the main steps are: understanding the environment, characterizing the workload, modeling the workload, validating and calibrating the models, predicting the performance, analyzing the costperformance plans, and suggesting actions.
doi:10.1109/mitp.2002.1046642 fatcat:wrmkxqoigrcbbd6626kiiyjuwq