IBM's Timothy Sipples recently calculated the optimum number of mainframes needed in a typical data center. His conclusion: Few data centers need more than two System z machines. "Mainframes are not like distributed servers," he said. "You simply don't need many System z machines; they provide uniquely ultra-concentrated computing throughput and quality. For perspective, even a single System z mainframe is quite arguably superior in delivering higher availability and reliability than multiple clusters of distributed servers. Also keep in mind that you do not need separate physical machines for development and testing- LPARs accomplish that."

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