Product Documentation

Clustered License Servers

Jan 10, 2012

Cluster servers are groups of computers that are combined to increase availability, reliability, and scalability. Microsoft clustering functionality exists in Windows Server 2003 and Windows Server 2008. Clustering the license server lets users continue working during failure situations without interrupting their access to critical applications. When the active node in a cluster-enabled license server suffers from hardware failure, failover occurs automatically. Resources are available again in a few seconds to a few minutes.

A typical cluster configuration has, at a minimum, one active and one passive (backup) server. When the active server in a cluster fails, the ownership of the resources in the cluster are transferred to the backup (passive) server. Typically, users cannot detect when one server in a cluster fails over to another.

When the active node of a clustered license server fails, there is no impact on users connected to the Citrix product. The product may briefly enter the licensing grace period and an event may be written in the product’s event log.

Citrix Licensing supports clustering the license server with two servers in a cluster and a shared drive. That is, you can cluster the license server in a two-node Microsoft Cluster in an Active/Passive Microsoft clustering configuration.

Important: License Server VPX does not support clustered license servers. You can use the High Availability (HA) feature on XenServer 5.6-6.0.

Citrix Licensing in a Cluster

Like most clusters, a private network is used to send heartbeats, commands, and state information between the nodes of the cluster. If the connection is interrupted, the nodes try to reconnect by the private network first, then the public network. The following diagram illustrates a cluster-enabled licensing deployment:

Figure 1. Communications in a clustered licensing environment

Only one node can utilize the resources in a cluster at any given time. If you already deployed Citrix Licensing and you want to migrate your deployment to a cluster-enabled server, keep the following points in mind:
  • Because you already generated license files that reference a specific server name, you must either give the cluster the same name as the original license server or rehost your license files with the new name of the license server cluster.
  • Cluster names are always ALL UPPERCASE. Host names in license files are case-sensitive; therefore, the cluster names must be all uppercase in the license file. If they are not, you must rehost your license files with the correct capitalization of the names.
  • You must point all product installations (for example, servers running Citrix XenApp) serviced by the old license server to the new license server cluster. Change product communication settings so that they use the name of the cluster as the license server name. For information about editing product-side communication settings, see the product’s documentation.

Opening the Console or Running Commands

All licensing administration features available in standard deployments are also available on clustered license servers, including the management console and the ability to run license administration commands.

Open the License Administration Console in a cluster by browsing to:

http://clustername:web service port

Where clustername is the name of the cluster and web service port is the port number for console communications (the default port number is 8082).

You can run many license administration commands using the argument -c @clustername to specify the location of the license file(s) in the cluster. For example:

lmreread -c @clustername