The Unix operating system, and the servers which provide the base to run it, are still the heart of many of the world's mission-critical enterprise data center infrastructures. It provides a combination of performance and stability as yet unmatched by any other operating environments. While the Unix server business has lost much of its glamour in the face of assaults from Windows, Linux, and the cloud, there is still plenty of life -- and growth -- in the business, although for the foreseeable future that growth will be enjoyed only by IBM (NYSE:IBM).