This document summarizes performance testing of a virtual Linux desktop cloud service running on an IBM System z server. Thousands of virtual desktop clients were able to concurrently access an eyeos open source web desktop platform running on Linux on System z. The results validate that a shared all-Linux platform using z/VM virtualization can efficiently support thousands of concurrent desktop users using CPU, memory, and I/O resources. Rational Performance Tester was used to simulate users accessing files and browsing web pages from their virtual desktops to test the scalability and response times of the System z configuration.