In my last post, I talked about our plans of moving XenApp farm settings, server settings and session policies into Group Policy Objects. This time, I want to describe our plans on a related topic: how to migrate XenApp 4.x farms into this new management model.
XenApp 4.5 Administrators have two options to migrate their farms: either upgrade the existing farm over time, running the farm in mixed-mode; or create a new farm and move users and applications over time. 
The mixed-farm approach seems to be the easier of the two, but it has an important drawback: the migration cannot be staged. The recommended first step is to upgrade the Zone Data Collectors, which in turn affects all users and applications in the farm. If anything wrong happens – which is usually detected once users start to login and use their applications - there is no way to rollback without creating a farm outage.
The new farm approach is safer, as it allows Administrators to perform an “in-production” validation, migrating users and applications to the new version over time. The old production farm is not touched, which allows quick rollback of users to the previous farm if anything wrong is detected.

However, creating a new farm from scratch is not realistic in many environments. The reasons:

  • Farm configuration documents may not exist, or be out-dated.
  • Not sufficient hardware to maintain both farms in parallel. Servers have to move from one farm to other over time.
  • The migration is not transparent to end-users. If a single Web Interface is used, it will list applications as “Application (Old Farm)” and “Application (New Farm)”. If a separated WI is used, then users must configure browser and PNA to use another URL.

We do not plan to support mixed-farm migrations when we move XenApp configuration to Group Policy. Instead, we will focus on the issues above, creating the necessary tools to facilitate the transfer of configurations, users and servers from farm to farm.
This is the plan:
The first step is to create a new farm, installing a new Data Collector and creating a new IMA database. Infrastructure servers (License, Database, Edgesight, etc) may be shared between the old and new farm. The next step is to launch the Migration Wizard and go through the following steps:

  • The migration tool wizard will ask information about the old farm (address, authentication). You may chose to export all the old farm data into an XML file and modify it before importing the data in the next steps.
  • The wizard will ask the new farm information. It will then convert session policies, farm and server settings into Group Policies, and automatically associate GPOs with the new farm Organizational Units.
  • If the old farm contained multiple application silos, the wizard will ask for a server that represents the old farm silo, and create a Group Policy Object containing that server configuration. The wizard will then associate that GPO with the OU representing the Application Silo in the new farm configuration.
  • You will be able to select a list of “in-production” test users. The new farm will only enumerate applications to users in that filter list, regardless of the Application object configuration.
  • Add the new farm in your Web Interface sites. Web Interface will suppress enumeration of applications coming from multiple farms, based on configuration. This change will make the migration process completely transparent to end users.

At this point, you will have a fully configured, although empty new farm. Over time, you will:

  • Add more users to the new farm filter
  • Remove servers from the old farm
  • Upgrade XenApp software in the server (or re-image)
  • Assign the server to the new farm Organizational Unit.

This method is very flexible, you may stage the process based on application silos, zones, users, or any combination of these. The migration tools provided here are also very useful for other use-cases, such as replication of settings between test and production environments.

This plan is still on the drawing board, please feel free to comment and raise scenarios where you believe it wouldn’t meet your needs. Note that this is planned for the next major release after project Delaware, therefore still a long way in the future.