How to Calculate Megacycles per Mailbox


Topic Last Modified: 2005-05-10

To calculate how many users a server can support, you must first determine your current usage profile. You can calculate a usage profile by using the following two key metrics together:

  • Megacycles/mailbox   Megacycles per second, per mailbox. The raw processor usage required per mailbox that is measured during the peak two-hour period on a production server.

  • IOPS/mailbox   Input/output per second, per mailbox. The raw database (DB) disk usage (input/output per second) required per user that is measured during the peak two-hour period on a production server. This metric does not include transaction log input/output (I/O) operations. For detailed steps about how to measure IOPS per mailbox, see How to Measure IOPS per Mailbox.


If the users in a company are diverse usage requirements, you may have to measure usage profiles separately for different groups of users. For example, the sales engineers may have a different usage profile than the local marketing group. Having separate measurements is helpful only if the groups of users are significantly different.

  1. Select a production server with a typical user load.


  3. Calculate the average CPU usage (percent) from the data you obtain in Step 2.

  4. Calculate your current megacycles/mailbox as described in the following formula:

    megacycles/mailbox = ((average CPU usage) × (speed of processors in megacycles) × (number of processors)) ÷ (number of mailboxes)