Citrix XenApp can scale to meet the most demanding and complex business environments. This information helps to maximize the business requirements to provide a scalable and high availability infrastructure while delivering on-demand access to applications and information for the enterprise.  The requirements and associated solutions are consistent with the business needs and challenges that are common to most large scale organizations.

How much storage is needed for the Citrix Datastore?

The Database file size during initial farm creation is around 1184 KB. Adding a server to the farm required 88 KB.
Application publication with 10 Citrix servers with 500 users with default icon required 296 KB.
Application publication with 10 Citrix servers with 5 user groups with default icon required only 40 KB.
Application published in 32-bit color icon required 24 KB. Application published in 256-bit color icon required 48 KB.
Creating a worker group required 2 KB. Creating one load evaluator required 8 KB. Apply load evaluator for 10 servers required 16 KB.

Creating a farm with 1000 servers and 1000 published applications, 100 worker groups to serve as applications silos and 10 load evaluators, the IMA data store size requirement will be approximately 500 MB.

A published application with 32-bit icon consumes about 65KB of memory  on the data collector. The average user session consumes approximately 1.6 KB of memory on the data collector. The average Citrix server consumes approximately 210 KB of memory on the data collector.

Resource utilization of the License server?

A single license server can adequately handle the load placed on it by a thousand servers and tens of thousands of users.  The license server uses approximately 4.5KB of memory for every session license and 39KB of memory for every start-up license that is in-use. The license server is capable of processing 248 license check-out requests per second. In a given scenario with all users logging in over the course of 30 minutes, a single license server would be able to handle 446400 users.

When a XenApp server comes online, it establishes a static connection to the license server and checks out a Citrix startup license. Also every 5 minutes, the XenApp servers will contact the license server to ensure it is still available. This action consumes 1.68 KB of bandwidth and occurs for every server in the farm. Once a startup license is checked out, the server holds this license until it is taken offline or the license server location is changed.

When a client logs in, the XenApp server requests a license from the license server on behalf of the client. The amount of bandwidth consumed for a license check-out request or check-in request is 1.04 KB. Every 5 minutes, each XenApp server exchanges a heartbeat with the license server to check license server’s availability and it requires the bandwidth of 366 bytes for each server. The timing of the heartbeat is based on the start time of the IMA Service.

Web Interface server requirement

The number of users that a single Web Interface server can support is dependent on the processor speed rather than the number of processors in the system.  Web Interface server with Windows 2008 R2 / IIS 7.0 / Intel Xeon X3360 dual core 2.2 GHz processor with 2GB of RAM is able to handle 9 user requests per second. Approximately the Web Interface server can service 30,000 users per hour.

Knowing Group Policy Management refresh intervals

When Citrix policies are managed from the AD domain group policy, the sequence of policy refresh and update is as follows:

1. change is made on the GPMC
2. within 1½ to 2 hours, member servers pull and apply updates
3. every 3 hours, AD replication occurs between domain controllers
4. within 1½ to 2 hours, remote member servers pull and apply updates

Resource utilization of IMA Communications

After the XenApp server starts, every 30 minutes the local host cache will perform a consistency check to ensure it is in sync with the Datastore. Every 60 seconds the Data Collector will send an IMAPing to  ensure the  member server is alive.

Planning worker groups

Adding 200 worker groups will increase 2.5 seconds for the management console discovery time, while 500 worker groups increase the discovery time by 4.2 seconds. Worker groups and their memberships are cached in memory in every IMA service for performance. This will increase the memory consumption of about 8 KB for every worker group in the farm.