Migrating SSAS away from SQL for a Fully Distributed Installation

If your organization is in need of migrating your Discovery Center installation from a shared SQL/SSAS deployment to a deployment with separate SQL and SSAS servers, either to follow a standardized infrastructure policy, or to gain performance improvements when processing reporting, this knowledge base article will provide the required instructions to successfully make this change in your environment.

Because of the nature of the Discovery Center application architecture, splitting SSAS and SQL has implications for the host environment which must be configured correctly to continue to work. These steps are documented in Appendix 7 of the installation guide titled "Additional Configuration for Fully Distributed Configuration". These steps should be carefully studied before starting to carry out this migration.

The number of SQL specific configuration elements in the Discovery Center application mean that manually re-configuring the application is time consuming and risks human error. Due to this the safest and easiest way to ensure correct configuration is to perform a custom uninstall of the Discovery Center application and reinstall using the updated SQL and SSAS server information.

Note: If you have more than one Discovery Center installation using the same SQL/SSAS server, you will need to repeat the re-installation steps for each Discovery Center.

Procedure

For data safety purposes, it is important to begin by backing up the SQL Discovery Center database.
Perform a custom uninstall of the Discovery Center application by opening Control Panel -> Programs and features, selecting the Discovery Center application in the list of installed programs, and then selecting the "change" option.
When you activate the change option, you will be shown a dialog sequence that will let you select "Remove" as an option. This will lead to a dialog where you can deselect the option to remove the SQL database on installation removal. Deselect this option and then let the uninstall continue.
Reinstall the Discovery Center application and enter the details of the existing SQL Database and SSAS instance at the relevant points in the installation wizard.

Installation steps can be found in the installation guide document in the zip folder containing your Discovery Center release version.

Use the command line installation method with logging enabled which will enable you to identify any issues that might occur with the installation.

This can be seen in Appendix 5: "Command Line Installation" of the installation guide.
You will be notified that the database already exists and must confirm that you wish to continue the installation using this database.
For a fully-distributed configuration where Discovery Center, SQL Server and SQL Server Analysis Services are each installed on separate host servers, additional configuration is required to allow authentication between each component.

In order to produce reports the Discovery center must be able to access data from SSAS via SQL Server, creating a situation known as Double Hop Authentication requiring SQL Server to present credentials from the Discovery Center service accounts to the Back End Tier.

Kerberos must be used support double-hop authentication, requiring certain pre-conditions to be met by the operating environment and specific configuration steps to be taken.

Appendix 7: "Additional Configuration for Fully Distributed Configuration" of the installation guide provides the steps required for configuring Kerberos, and should be used to configure the authentication.
Once the installation is complete, it is important you check Discovery Center functionality.

Ensure the following aspects of the system function normally:
- Confirm that the Discovery Center website loads without any errors.
- Confirm expected indexes are available.
- Process the reporting database.
- It is possible to generate reports.

If these tests pass, you can confirm that the installation was a success.