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How to Calculate Mailbox Server CPU Requirements


Topic Last Modified: 2005-05-10

After you have determined your usage profile (megacycles/mailbox and IOPS/mailbox), you can calculate your CPU and disk subsystem requirements. This topic explains how to calculate CPU requirements. For detailed steps about how to calculate disk subsystem requirements, see How to Calculate Mailbox Server Disk Subsystem Requirements.

Before you perform the procedure in this topic, consider the following recommendation:

It is generally recommended that you use a 4-processor (2.8 GHz) server for high-end server configurations. The recommended hardware does not take into account other performance factors, such as network capacity, server memory, and cache sizes. However, by using the example usage profiles, you can estimate if a server has sufficient CPU and disk capacity.

  • To calculate the maximum number of users your processor can support, multiply the total processor megacycles by 0.80 and divide by your current megacycles per mailbox.

    Nmax users = 0.80 × (number of processors) × (speed of processors in megacycles) ÷ (current megacycles per mailbox)

  • Similarly, to determine if your server has sufficient megacycles for the number of users you want to put on the server, multiply the number of users by your current megacycles/mailbox, and then divide that result by the megacycles of the server (the number of processors multiplied by the speed in megacycles), shown below. If the value is less than 0.80, the server can support the number of users. Do not exceed 80 percent usage, or the server will be overloaded.

    CPU Usage = ((number of users) × (current megacycles per mailbox)) ÷ ((number of processors) x (speed of processors in megacycles))

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