Performance by Design: Computer Capacity Planning by Example

Chapter 13. Queuing Models with Multiple Classes

Introduction

The real power of performance models becomes evident when they are used for predictive purposes. In performance engineering, models are essential because of their ability to predict adequately the performance of a particular system under different workloads. Real-life systems experience a wide variety of customers (e.g., experienced heavy users, novices, web surfers, e-mail users, bank transactions) with different resource usage profiles. Actual workloads do not tend to be a single class of homogeneous customers. Typically, each customer differs from every other customer. However, it is impractical to model each customer’s individual idiosyncrasies exactly. Rather, customers are grouped ...