Upgrading an Exchange organization: Key considerations and best practices

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Are you planning to move your Exchange Server to a newer version? This article helps you understand the key considerations and best practices for moving an Exchange Server to an upgraded environment from the standpoint of an on-premises deployment.

On-premises Exchange deployments can be done based on two strategies, namely upgrade and cross-forest migration. At a high level, upgrading an Exchange organization involves migration of the mailboxes and public folders from the existing Exchange Server to a newer version, whereas, cross-forest migration involves consolidation of two or more Exchange Server organizations into a single organization.

Nonetheless, the prerequisites and best practices for moving to a new Exchange Server setup, as outlined in this article, are valid in both scenarios. Further, the article illustrates the specific aspects such as deployment and database migration largely in the context of Exchange Server 2016.

Before you read further, here are a few important points to consider:

  1. Moving an Exchange Server to a later version, also referred to as upgrading the server, involves two steps, namely, the deployment of Exchange to a new server and migration of data from the legacy server to the new server. For this, you would need to check the coexistence of both servers. Exchange 2010 can coexist with 2013 and 2016, but it cannot coexist with 2019. If you are upgrading from Exchange 2010, you will firstly need to migrate to 2013 or 2016, decommission the Exchange 2010, migrate to 2019, and decommission 2013.
  1. In-place upgrade of Exchange Server is not possible. Also, it is not advised because of the complex architecture of Exchange Server and the significant disparity between any two versions of Exchange.

Key considerations before upgrading to Exchange Server 2016

Before you install Exchange Server 2016, you must fulfill the following prerequisites:

  1. Configure hardware and OS as per the role requirements
    Ensure that you have a 64-bit OS running on 64-bit hardware, as Exchange Server 2016 is available only in a 64-bit version. Also, use a full GUI mode operating system, as Exchange Server 2016 doesn’t support the Nano Server or Server Core mode in Windows Server. You can install and run Exchange Server 2016 on Windows Server 2012 R2 (any edition) or higher operating system. Use the Exchange Server Role Requirements Calculator to calculate the hardware requirements.
  1. Check and upgrade Active Directory and domain controller

Perform a due diligence on the domain controllers and global catalog servers in the Active Directory forest before initiating the Exchange upgrade process. For upgrading to Exchange Server 2016, ensure that all domain controllers, including the Schema Master and global catalog servers, are running a minimum Windows Server 2008 R2 version. This is crucial to make these servers accessible to Exchange Server; otherwise, the installation process will fail.

Further, check and ensure that the AD functional level must be Windows Server 2008 R2 or higher when you are upgrading to Exchange Server 2016.

  1. Check the Active Directory health

Check the health of Active Directory before initiating the Exchange upgrade process because Exchange relies on Active Directory configuration for routing the messages. You can use PowerShell cmdlets to check the health of individual components of Active Directory.

For instance, the Get-ADReplicationFailure cmdlet is used for finding out the list of failures associated with a particular domain controller or Active Directory Lightweight Directory Services (AD LDS).

Example using PowerShell:

C:\PS>Get-ADReplicationFailure -Target corp-DC08

The above command fetches data for Active Directory replication failure for corp-DC08.

Example using PowerShell:

C:\PS>Get-ADReplicationFailure -Target Canada -Scope Site

The above command gets the data for Active Directory replication failures from all the domain controllers in the site “Canada.”

  1. Check the domain controller health

It’s crucial to evaluate the health status of domain controllers in a forest, in general, as well as when you plan to migrate your Exchange organization.

Use Dcdiag, a Microsoft Windows command-line tool, for analyzing the state of domain controllers. It comprises a framework for executing the tests for verifying the functional state of domain controllers on a single server, enterprise, or site. Here’s how you can use Dcdiag:

  • Click Start, right-click command prompt
  • Run as administrator

The following examples illustrate some of the Dcdiag commands:

dcdiag /s:DC25 This command uses /s: switch to run all the DC tests on a server named DC25
dcdiag /s:DC25 /f:d:\is\dcdiag_test.txt This command uses /f: switch to save all the DC test results for a server named DC25 in a text file
dcdiag /s:DC25 /a This command uses /a: switch to run the DC tests on all domain controllers at once
dcdiag /s:DC1 /q This command uses /q: switch to display only the errors after running the DC tests on a server named DC25

Upgrading Exchange

  1. Upgrade the existing Exchange Server to support coexistence

In order to upgrade the existing Exchanger Server version “X” to a newer version “Y,” the current Exchange Server environment must meet a certain baseline specification to allow it to coexist with the new version to which you are planning to move.

The following are the supported coexistence scenarios for Exchange Server 2016 and 2019:

Exchange Server 2016 »

Exchange Server 2010 Exchange Server 2010 Service Pack 3 with Update Rollup 11 or later on all Exchange 2010 servers, including Edge Transport servers
Exchange Server 2013 Exchange Server 2013 Cumulative Update 10 or later on all Exchange Server 2013 servers, including Edge Transport servers

Exchange Server 2019 »

Exchange Server 2010 Not supported
Exchange Server 2013 Exchange Server 2013 Cumulative Update 21 or later on all Exchange Server 2013 servers, including Edge Transport servers
Exchange Server 2016 Exchange Server 2016 Cumulative Update 11 or later on all Exchange Server 2013 servers, including Edge Transport servers

Best practices for migrating to Exchange Server 2016

Along with the prerequisites, there are a few “best practices” that could help you to upgrade your Exchange server organization in a seamless manner. The following are some of these important best practices, tabulated and categorized, to facilitate a smooth upgrade of Exchange organization:

Upgrade Aspect Best Practice
Hardware Use Exchange Server Role Requirements calculator to determine the hardware requirements for Exchange deployment. In general, for upgrading to Exchange 2016, choose more number of cores when possible because Windows Server 2012 and 2012 R2 licensing is based on processors rather than cores.
Server Sizing Create a diligent plan for server sizing, virtualization, and high availability. Refer to the Exchange 2016 Preferred Architecture (PA) for the Microsoft Exchange Engineering Team’s best practices for an optimal deployment architecture of Exchange 2016. Also, use the Microsoft Exchange Deployment Assistant to get specific technical guidance.
Domain Controller For upgrading to Exchange Server 2016, upgrade all the domain controllers to a minimum Windows Server 2000 R2 version
Active Directory Have a detailed list of all the AD domains in which Exchange Server 2016 will be installed, or recipient objects will be created. Set the domain functional levels to a minimum Windows Server 2008 R2 (or higher if possible) for all these domains.

Higher domain functional levels, enabled with higher versions of Windows Server, can enhance the performance of domain controllers by provisioning more memory to load the Active Directory database.
Coexistence Refer to Microsoft documentation on the Exchange Server build numbers and release dates to ensure that you have the latest information for meeting the baseline needs for a coexistence scenario.
Exchange Server Don’t install Exchange Server on a domain controller server. Though it is technically feasible, it is not recommended. This can hamper the performance of Active Directory by overconsumption of the memory by Exchange Server and its services. It is recommended to install Exchange into an Active Directory deployment site.
Certificates and Namespace It is important to plan out for the migration of certificates, including the third-party certificates, when you want to upgrade Exchange. Also, deploy a unified or combined namespace for the site resilient datacenter pair. And deploy dedicated namespaces for an individual datacenter. Refer to the Microsoft resource on Namespace Planning in Exchange 2016.
Cross-Forest Migration Migrate a limited set of user accounts to the new forest at a time to avoid confusion and allow the opportunity to test and build the trust between the different forests.

Also, enable directory synchronization between the forests to ensure that users moving to the new forest have access to the updated Global Address List (GAL) and that emails get delivered to the right Exchange organization.

It is advised to do a test mailbox move to test the mail flow and client access services on the new server.
Database Considering the complexity of cross-forest migration due to the number of objects and databases involved, and that you would be moving to a new AD forest, it is advised to have third-party tools to assist the process.

You can migrate Exchange to a new forest using the free Microsoft tools such as Active Directory Migration tool and Exchange Server cmdlets; however, it is a best practice to invest in a third-party tool to serve as a safety net when you have a costly and strategically important migration project lined up.

For example, if you need to migrate the mailboxes of a legacy server while moving the Exchange organization, you would need to mount the EDB, which is not possible without the AD and domain controller setup. Best EDB to PST Converter Tool can extract mailboxes from the offline EDB in PST files and export them to a live Exchange. This will allow you to attach any version of Exchange database.

Use of third-party tools is also highly recommended if you’re migrating more than a few hundred users, have very large mailboxes or considerable data in the Public folder.
Multiple-site Deployment Upgrade the Exchange Server on one site at a time if you are planning for a multi-site deployment. As a best practice, it is recommended to upgrade Exchange at Internet-enabled sites first, as they allow proxy functionality.
Legacy Server After moving the mailboxes to the new server, verify and ensure that no application or device is using the old Exchange Server. After that, “uninstall” the legacy server to remove it.

Closing notes

Upgrading an Exchange organization requires considerable planning for smooth execution and to avoid any unpleasant surprises. A key aspect of upgrading Exchange is to meet the various prerequisites before making the move, i.e., deploy and migrate to the new environment. Additionally, it is also important to consider the best practices for migrating Exchange, which can complement the standard procedure to ensure that you execute possibly the most-efficient approach. This article presented a collated view of all the key prerequisites and best practices for upgrading to Exchange Server 2016, but the same concepts apply to Exchange Server 2019.

During a migration, anything can go wrong, which could be either a missed prerequisite, issue during migration being hardware, software, or human error, which could render the Exchange server unusable. This is where a third-party application like Stellar Converter for EDB can come in handy to reduce the downtime, assist in the migration and minimize the administrative effort during issues where it could get lengthy to restore and bring alive an old server. This is because the tool can mount any Exchange Server database, export to PST and other formats, export directly to any version of Exchange Server online database or Office 365. This tool is the right companion during normal operations and migrations as it can get you out of a crisis.

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