One of the more common problems with Linux on System z proofs of concept has been the lack of understanding of performance and the inability to measure it correctly. Since the inception of Linux on System z, Velocity Software has been developing and refining a set of tools that provide the information that can be used to assess the viability of POC endeavors. The tools also provide a means to monitor systems when they are moved into production. In this presentation several case studies will be presented and analyzed to illustrate the concepts and practices of performance management of the Linux on System z systems. All examples will use Velocity Software's ESALPS product, the suite of tools they developed especially to measure and monitor the Linux and z/VM environment, as the measurement facility.