Sizing and Optimizing Terminal Services Environments

The Terminal Server can be sized to deliver high-performance terminal sessions by estimating the amount of resources each user will require and the number of users who will utilize Terminal Services. Performing frequent performance testing on the Terminal Servers helps generate accurate information on Terminal Server usage. You should perform performance testing during both peak and nonpeak times to ensure proper data collection. Increase memory and processors or introduce additional Terminal Servers as necessary. Understanding the users' resource needs and the number of users will help you decide how to specify the server hardware requirements and determine how many Terminal Servers you need to support the load.

Scaling Terminal Services

Scaling Terminal Services can be achieved by increasing server resources such as the number of processors and the amount of memory, as well as by increasing the number of servers that are servicing requests. When determining how to scale, also consider manageability, cost, and how end users may be affected if a server goes offline. For instance, using a greater number of lower-powered servers may increase manageability (such as updating applications, keeping up with operating system updates, and other maintenance), but if a server goes down, fewer users will be affected. The solution will vary depending upon your organization's needs and circumstances.

Another consideration is the amount of flexibility your organization requires. Using more instead of bigger servers gives more flexibility because of the redundancy, as well as the capability to take servers offline for maintenance. In this scenario, it is important to use servers with enough power to sustain slightly greater workloads during those times when other servers in the farm go offline.

Note

For more information on scaling Terminal Services, refer to Microsoft's "Windows Server 2003 Terminal Server Capacity and Scaling" whitepaper.

Adding Redundancy and Scalability to Session Directory

Using Session Directory server in Terminal Services farms is a great way to provide failover for user sessions. To avoid this service from becoming a single point of failure and scale it to meet the performance needs of the organization, you can configure Session Directory to run as a clustered service using MSCS. To create the cluster for Session Directory, do the following:

1.	Ensure that the Terminal Services Session Directory Server service is set to Automatic.
2.	Ensure that the following resources are available in the server cluster configuration: Physical Disk In addition to the quorum disk, the cluster will require a shared disk for the shared data. IP Address A static IP address that is accessible to all the terminal servers. Network Name A name that is resolvable from all the terminal servers in the cluster. Kerberos is required for all communication between the terminal server and the Session Directory server. Make sure to select Enable Kerberos Authentication and DNS Registrations Must Succeed before bringing the network name resource online.
3.	Select File, New, Resource. When the wizard starts, enter the name and description, and set the resource type to Generic.
4.	Click Next and accept the defaults.
5.	Define your dependencies. Specify the Physical Disk and Network Name resources.
6.	Define the Generic Service Parameters. Specify the service name (TSSDIS) in the Service Name box, and check the box next to Use Network Name for Computer Name.
7.	Configure Registry Replication. Click Add and type System\CurrentControlSet\Services\Tssdis\Parameters.
8.	Click Finish.
9.	Bring the new service resource online.

Note

For more information on MSCS, refer to Chapter 31.

Optimizing Terminal Services Performance

Optimizing Terminal Services is a challenging task because of the complexities in any environment. Hardware resources, applications, usage, the number of users to support, and much more can affect how well Terminal Services responds to users. There are rarely cases where there is one "silver bullet" that can improve overall performance; it takes a combined approach. For instance, from a user perspective, video, color depth, audio redirection, printer redirection, and encryption level all affect how well a system performs.

The following are best practices for ensuring that the Terminal Services implementation runs as efficiently and effectively as possible:

• Limit users to a single session.

• Log off disconnected or idle sessions after a specified period of time.

• Use only Windows Server 2003 certified printer drivers.

• Use Windows Server 2003 certified applications and consult the vendor for specific application optimizations.

• Use Microsoft Operations Manager (MOM) or other operations management software to monitor the Terminal Services farm.

• For medium and enterprise deployments, use a separate server or group of servers with a fast disk subsystem to store user profiles.

• Consider using third-party Web browser pop-up blockers.

• Block Internet Web sites that use a lot of animation.

• Prevent users from installing applications such as games or desktop enhancements/themes.

• Automate Web browser cookie deletion.

Monitoring Terminal Server

The Performance MMC snap-in can be used to monitor Terminal Services and to gather session statistics. The two specific performance objects for Terminal Services are Terminal Services and Terminal Services Session.

The first object, Terminal Services, has only three counters: active sessions, inactive sessions, and total sessions. Gathering this session data and teaming it with information such as Server Memory\Available Bytes and Processor\% Idle can give an administrator a clear understanding of Terminal Server usage and load. This information can be used to determine whether additional resources or servers need to be added to accommodate load or enhance performance. One adjustment that may be made after taking readings from these counters is the implementation of disconnected session time limits to free server hardware resources for active sessions.

The second performance object, Terminal Services Session, can be used to monitor all counters available for a particular Terminal Server session. This object can be used to get accurate statistical information, such as how much memory and processor time the average Terminal Server session uses. Be sure to monitor network interfaces for available bandwidth to ensure that the Terminal Server is not creating a bottleneck between clients and other back-end servers.

Using Windows System Resource Manager to Control Resources

With Windows System Resource Manager (WSRM), you can limit the amount of CPU and memory an application can use. In the Terminal Services environment, you can assign distinct settings based not only on an application, but on a specific user or group as well. This helps to enforce consistency among user sessions and prevent rogue applications or sessions from negatively affecting other user sessions. For more information on using the Windows Resource Manager, refer to Chapter 35, "Capacity Analysis and Performance Optimization."