How to Calculate Mailbox Server Disk Subsystem Requirements

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

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.

Procedure

To calculate disk subsystem requirements

  • To calculate if the disk subsystem is adequate, multiply the number of users that will be on the server by your current IOPS/mailbox, and then divide that result by the total IOPS/second capacity that the disks provide. Your disk usage should be under 0.80, or the server will be overloaded.

    Disk Usage = ((number of users) × (current IOPS per mailbox)) ÷ (total IOPS/sec)

  • It is recommended that you calculate disk usage separately for each database. If all your databases in a storage group share a single logical unit number (LUN), you can calculate per storage group instead of per database, as shown below.

    Disk Usage (per database) = ((number of users in the database) × (current IOPS per mailbox)) ÷ (total IOPS/sec).