Cluster servers are groups of computers that are combined to increase availability, reliability, and scalability. Microsoft clustering functionality exists in:
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.
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 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 use 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 client access point the same name as the original License Server or rehost your license files with the new name of the License Server cluster.
- Host names in license files are case-sensitive; therefore, the client access point names must be the same case as the host names in the license file. If they are not, you must rehost your license files with the correct capitalization of the names. You can use the Failover Cluster Manager to ensure the client access point name matches the host name specified in the license file. Note: Cluster and host name case is not an issue if you use Studio in XenDesktop or the Simple License Service (from the Start menu on your License Server) to download your licenses.
- You must point all product installations (for example, servers running Citrix XenDesktop) serviced by the old License Server to the new License Server cluster. Change product communication settings so that they use the name of the client access point as the License Server name. For information about editing product-side communication settings, see the product's documentation.