Capacity Planning for Web Performance: Models, Metrics, and Methods

The modeling of the Internet has become extremely important in recent years as it continues to grow in leaps and bounds. Network architects have to become very aware of the performance issues when they design networks that will be integrated into this elaborate spider of clients, servers, routers, and switches. The issues in the modeling of global networks are extremely complex and involve very advanced mathematical techniques in order to do the job effectively. The authors of this book however have written an introduction to Web modeling that is written at a level appropriate for network designers and the beginning modeling engineer. They employ Excel spreadsheets and C code to assist in the modeling efforts, and these packages are available on an accompanying CD. After a brief discussion of the issues concerning capacity planning, Web server, Intranet, and ISP performance in Chapter 1, the authors move on to defining and characterizing client/server systems in the next chapter. After a brief overview of the history of the Internet, they discuss LANs and WANs, and a quick treatment of protocols. The TCP protocol is considered in somewhat more detail because of its importance in network performance. The quantitative analysis of performance in client/server environments is begun in chapter 3, wherein the authors begin with communication-processing delay diagrams to illustrate how requests spend time at each resource. This is done for both a 2-tier and a 3-tier C/S architecture, and the authors detail how disk subsystems contribute to the service time at a disk. An elementary iteration technique is used to compute the disk utilization. A very interesting and detailed discussion of the RAID-5 disk array is given. Some elementary queuing theory is discussed, using the assumption of flow equilibrium. A simplified summary of the utilization, forced flow, service demand, and Little's laws is also given without resorting to complicated mathematics. Performance issues in Intranets and Web servers are the topic of the next chapter, and most importantly, the authors outline the differences between HTTP 1.0 and HTTP 1.1. The role of the proxy server and its contribution to performance is also discussed, along with Web cluster architectures. The authors first mention the role of burstiness in this chapter, but do not give an in-depth mathematical discussion. In chapter 5, the authors give a step-by-step methodology for capacity planning for C/S systems. Workload characterization, data collection issues, model validation, and forecasting are all discussed quantitatively with more details in later chapters. How to characterize the workload quantitatively is the subject of the next chapter, in terms of a business, functional, and resource-oriented methodology. The authors discuss briefly workload models from a non-mathematical point of view, with parametrized models given the emphasis. The calculation of the parameters is given a more detailed and mathemat

Easy enough for any IT person to understand yet detailed enough for real world capacity planning. It doesn't favor any hardware or software but drills in on ways to measure any of them.

If you thought Web architectures were too complex for modeling, you are wrong ! This text explains all possible major components of Web transactions - from TCP/IP, http, CGI, proxy and cache servers, browsers, and networks, in detail. It also explains and adapts various utilization, queue, and response time models to performance analysis and capacity projections. This text is outstanding as both a tutorial and reference. Particularly useful are many real world examples with solutions based on the models. The models are available as Excel worksheets. I recommend this text for all who are serious about designing Web applications that scale well and that are responsive to users. --- Ted Hruzd, performance analysis / capacity planning in the securities industry since 1984; platforms: Tandem, HP UX, and NT --- [email protected]

This is a great book that really simplifies the modeling of complex performance problems. The included CD-ROm contains several tools that allow prediction of throughput, response time, and bottlenecks.

As a technical consultant in interactive solutions for a large systems integrator, I am confronted on every project with the capacity planning issues related to e-comm applications. The estimation of sizing and performance are often considered "too complex" and lead to high-level deliverables that eventually cannot serve as an acceptable basis for service level agreements in a company. This book, gives an a methodology that leads to metrics that model your system. The approach is practical and the accompanying examples (and excel spreadsheets) are very concrete. As I don't have the time to go back to the gory details of queuing theory, I find the formulas well explained and helpful to derive the required SLAs and other metrics needed to roll out a system where the performance is understood. Really useful!