Compaq ProLiant 6000 Software Manual page 11

ECG052.0897
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Introduction
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This section of the paper will focus on the performance of Microsoft Exchange Server in testing.
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Four main server resources will be addressed:
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Processor subsystem -- all the server's CPU resource, whether a uniprocessor system or a
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multiprocessor system
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Disk subsystem -- all the server's disk storage resource, including controller type and number
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of drives in a RAID set
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System Memory -- all the server's memory resource, but not including cache memory on
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processor boards or drive arrays. This is the amount of RAM installed in the system
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Network – the server's network connection and its capacity, performance and effect on
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Exchange Server response time
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The cardinal rule to remember is this: If a subsystem is not a bottleneck, then adding more of
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that resource will not increase capacity. In all likelihood, adding more of a non-bottlenecked
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resource will provide minimal improvements in response time, but not provide any additional
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system capacity.
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When analyzing the different resource areas of a server (CPU, memory, disk, and network), it is
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also important to understand the performance-versus-cost trade-offs involved. If the addition of a
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resource provides an incremental ten-percent performance benefit, the cost must be weighed
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against the total system cost and the overall importance of the performance benefit to your
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organization. The important consideration is whether or not the performance gain justifies the
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additional cost.
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Remember that costs can also come in the form of increased management and support overhead,
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system complexity, or more potential points of failure. An example of this with Microsoft
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Exchange is the question of adding a third processor. Exchange may benefit in response time to
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users by five to ten percent, but no additional system capacity (ability to handle more users) is
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. . achieved. In this case, it is unlikely that the additional cost for a processor is justified. Similarly, a
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large, high-end RISC-based system may provide performance gains of from five to ten percent,
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. . but may cost as much as 200% of the price of a Compaq ProLiant server. Again, the question is:
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Does the possible performance benefit justify the cost premium?
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