Exchange 2013 Sizing — Tips and Tricks Part 1

While roughly 35% of the Microsoft e-mail user base has possibly moved to Office 365, many of our clients continue to run an on-premises Exchange Server environment.  As the time continues to tick down to the end of Exchange 2007 support, you may be anticipating an Exchange upgrade in the coming year.

We’ve recently performed a number of sizable migrations to Exchange 2013.  A key part of the design process is determining sizing for your Exchange (soon to be Exchange 2016) environment and supporting utilities.  The continuing changes in the software and hardware capabilities of an Exchange deployment sometimes make for conflicting sizing guidance from one version to the next.


Starting with Exchange 2007, Microsoft created the the Exchange Server Role Requirements Calculator to assist in sizing your Exchange deployment.  This tool automates the various sizing computations required, based on various functionality, activity, and availability inputs.

The Requirements Calculator has not necessarily gotten easier to use (60-ish potential inputs for the 2007 version, up to around 100 for 2013) over the years, as Exchange Server has gained new and improved functionality.  The shift from distributed to consolidated Exchange server architectures has also added some new sizing complexities.

The calculations automated by the Requirements Calculator are amply detailed in various Exchange Team postings.  Some sizing aspects are not covered by the Requirements Calculator, so understanding the full process is essential to designing your Exchange environment.  Let’s focus however on what is addressed by the Requirements Calculator, and some tips to make your sizing exercise a bit easier.

Getting Started…

Basic requirements, including:

  • High availability
  • Number of database copies
  • Preferred disk volume free space
  • Database size limits
  • Global changes to data sizes and IOPS

…are entered in the Environment Configuration section.

Environment Configuration Section

Many of these settings are self-explanatory, and many of the defaults can be accepted.  To make the next few steps easier:

Initially limit the size of the deployment to a multi-role, non-high availability deployment.  While you definitely should deploy Exchange in a highly available, multi-site design, reviewing and rightsizing the entire environment is made simpler by limiting the calculator to 1 server at the start.


Enter the desired free space for database volumes greater than 5%.  I’ve seen many clients run with < 5% free space on a database volume, but that doesn’t make for a restful system administration experience.  For our scenario, we’ll specify10% free space.

vol free space

Configure a default database size to match your restore goals.  While it’s technically possible to do an Exchange 2013 deployment without traditional data backups, many Exchange admins still prefer to do so.  Configure this setting to match your database restore SLAs, eg) run the database no larger than the size you can restore in the amount of time you’ve agreed to with the business.

DB size

In the next part, I’ll explain how to determine activity levels and turn those into Exchange Server resource requirements.

Planning an Exchange Server upgrade and looking for design assistance?  Let’s talk.

Phone: 312-602-4000
222 W. Adams
Chicago, IL 60606
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