Introduction

By default, in a XenDesktop farm the initial Desktop Delivery Controller (DDC) installed is the farm master with specific duties as the data collector, performing desktop resolution operations during desktop launches, and managing the hosting infrastructure. This single server has the role of Data Collector and Controller. When there are multiple servers in a farm, it is often desirable to separate the functions of Controller and Data Collector by delegating these functions to different servers. These other duties can be better performed by other Desktop Delivery Controller machines in the farm, leaving the farm master machine to concentrate on its own role requirements.

To separate the roles, the actions to be taken fall into two parts:

• Ensure that a particular machine is chosen to be the farm master

• Ensure that unnecessary duties are not performed by that machine

Controlling Farm Master Selection

Each Desktop Delivery Controller machine in the farm can potentially become the farm master in an election process. This election process can be influenced by settings on the various server machines, and one (or more) machines can be indicated as preferred as being farm master, and other machines only take on the farm master role if the preferred machines are unavailable. This preference indication is achieved by use of registry entries on the various server machines. Each machine can be configured to have one of four possible settings:

• Master – servers with this setting are preferentially chosen as the farm master. Often, only one server in the farm would have this setting.

• Backup - servers with this setting are preferentially chosen as the farm master when the master server is unavailable.

• Member - servers with this setting are normally not the farm master, but can assume the farm master role when none of the master or backup servers are available.

• Slave Only - servers with this setting are not eligible to be the farm master.

To configure a server machine to one of these settings, perform the following steps.

Caution! This procedure requires you to edit the registry. Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Back up the registry before you edit it.

1. Set the HKLM\Software\Citrix\IMA\RUNTIME\UseRegistrySetting DWORD registry entry to 1

2. Set the desired master ranking value in the HKLM\Software\Citrix\IMA\RUNTIME\MasterRanking DWORD registry entry to one of the following values:

• 1 indicates ‘Master’

• 2 indicates ‘Backup’

• 3 indicates ‘Member’

• 4 indicates ‘Slave Only’

3. Restart the server

Controlling Brokering Duties on the Farm Master

The main set of duties that can be avoided on the farm master DDC server are those associated with managing the status and operations of individual Virtual Desktop Agent (VDA) machines. This can be achieved by setting a registry entry on the farm master server to limit the number of VDA ‘worker’ machines that the farm master agrees to administer. Again, this involves changing the registry so a backup of the registry is advised prior to making any changes. To limit the number of VDA worker machines allowed to register with a DDC server machine, and so be directly administered by that DDC server, set a value in the DWORD registry entry HKLM\Software\Citrix\DesktopServer\MaxWorkers on the DDC server to a particular value. The smaller the value in the registry entry, the fewer worker machines the server can accept, down to a value of zero indicating that the server cannot accept registrations from any VDA ‘worker’ machine, which forces all the VDA worker machines to register with other DDC server machines in the farm.

Note: Distributed farm deployments of XenDesktop are not supported. There is only one IMA Data Collector per farm. It is recommended to create multiple farms for geographically dispersed deployments.