Consolidation of Intel-based servers is a well-established strategy for reducing the running costs and management costs of enterprise IT systems. But if IBM has its way, more and more organisations will begin to explore the potential benefits of consolidating servers on the mainframe. Many enterprises continue to have mainframe systems at the heart of IT, running established mission-critical applications. And much of the needed server consolidation can best be applied to the growing army of Intel-based systems that sit around them. These systems run a variety of applications, from routine file and print services to the more complex applications and Web-based services needed for increasingly important e-business front-ends. Many of these applications can run under the Linux operating system as well as under Microsoft's Windows. Indeed, for some applications Linux is arguably the better option. This opens up an opportunity for IBM, the dominant mainframe supplier, to exploit the capability of its zSeries machines to run Linux as a native operating system, as well as to run partitions in which multiple virtual Linux servers can be mixed with existing mainframe applications on the same machine. Tackling the costing process IBM's argument for consolidating around the zSeries (formerly known as the System 390) is straightforward: Most enterprises already have at least one zSeries machine and, though undoubtedly more expensive as an initial purchase, they provide far better results in terms of total cost of ownership (TCO) over a lengthy period. Estimating the total cost of consolidating on the zSeries, therefore, is a matter of some importance and demands that IT managers collect some important evidence. IBM's approach is to compare the ways of running a specific application. So to start the costing process, the first job is to look at an application that's running on Intel-based servers and size it. There are some important variables to consider, depending on the platform used. People costs are obviously important and can vary dramatically, as can the cost of the software licenses required. How many heads? To determine people costs, the object is to arrive at a figure for the number of servers per head of staff directly involved in the IT function. In the Intel-based server arena, this will vary according to the tasks being run. For example, where there are many "clone" servers all running the same simple tasks such as file and print, it is possible to have up to 30 servers per head. At the other end of the scale, where servers are running more complex tasks, such as Web or applications services, this figure drops to ten servers per head or less. A general rule of thumb suggests that an Intel-based server environment running a tycouical mix of tasks under Microsoft Windows is considered excellent if it averages 15 servers per head. In a Risc/Unix environment, this figure drops to between two and eight servers per head, which appears significantly worse than that for an Intel environment, but there are other factors to consider. For example, the applications are usually more complex and critical to the business.