I recently got involved with a customer that said he had applied “the new feature pack” for XenApp 5 for Windows Server 2003 so that it could co-exist in a farm with XenApp 6 for Windows Server 2008 R2. When attempting to add servers to the farm, the new servers would fail. No servers could be added to the farm. The new builds were completely up to date, so why was this happening?

The reason that the servers failed is that you cannot run XenApp 6 in a mixed mode. No how, no way. Not with “the new feature pack,” not with any special hotfix, registry tweak, or miracle.

What happened in the above scenario is that the Data Store became corrupted. If you’ve never been through Data Store corruption, it means that you need to roll back to a previous version of the Data Store—or if that doesn’t exist, rebuild the farm. Not a pleasant situation.

In the past, Citrix supported mixed farms but strongly recommended against them. This is because administration is based on multiple versions of the consoles, options vary, differences in the Data Store schema, and most importantly, the user experience can vary within a mixed farm.

For example, if you run a mixed farm based on XenApp 5 for Windows Server 2003 and XenApp 5 for Windows Server 2008, you could configure Preferential Load Balancing on the XenApp 5 for Windows Server 2008 portion of the farm but not the older servers. However, a mixed farm based on this configuration should have Data Collectors that are based on XenApp 5 for Windows Server 2003, and the initial server in the farm must be based on XenApp 5 for Windows Server 2003 as well. A lot of fine details, true. It’s much easier to run two native farms and consolidate them via Web Interface.

With the release of XenApp 6, mixed farms aren’t supported at all. All of us techies have lived on the edge at times and gone beyond what is supported, but in the case of XenApp 6, don’t attempt it because it doesn’t work.

As you look to migrate to XenApp 6, which is crisply defined as a new farm with a new Data Store based on a clean server installation, consider using the XenApp 6 Migration Tool. It will enable you to transition some or all of your farm settings from your XenApp 5 farm to your new XenApp 6 farm. Your exported settings can be based on XenApp 4.5/5 for Windows Server 2003 HRP5 or XenApp 5 for Windows Server 2008. For more information about the XenApp 6 Migration Tool, please see:
-eDocs: http://support.citrix.com/proddocs/topic/xenapp6-w2k8/ps-migrate-xa6-wrapper.html
-Technical Guide for Upgrading/Migrating to XenApp 6: http://support.citrix.com/article/ctx124241
-XenApp 6 Upgrading/Migrating webinar: http://www.citrix.com/tv/#videos/1952
-XenApp 6 Migration Tool webinar: http://www.citrix.com/tv/#videos/2531

You can take your XenApp 5 settings with you to your new XenApp 6 farm with the XenApp 6 Migration Tool, but you can’t take the farm itself!

Jo Harder, Senior Architect