Server 2008 Terminal Services Part 9: TS Session Broker
As your environment grows in size, you’ll quickly begin finding how critical expanding that environment will be. Expanding that environment is important, but expanding it in such a way to provide load balancing and a bit of failover capacity is doubly so.
TS Session Broker is the tool that enables this load balancing capacity in your existing environment. In previous O/S’s, load balancing Terminal Servers involved creating the equivalent of a Network Load Balancing (NLB) cluster between hosts using a separate tool. The Terminal Services Session Directory service then managed that cluster to ensure cluster members were properly load balanced and clients got where they needed.
TS Session Broker is the update to TS Session Directory. It combines...
...the clustering functionality with the management provided by TS Session Directory and is easier to set up. Simply add the TS Session Broker Role Service to your Terminal Server Role. Then configure the servers to join a cluster by navigating to Terminal Services Configuration and double-clicking the item called “Member of farm in TS Session Broker”. You’ll need to check the box next to “Join a farm in TS Session Broker” and provide the server name of the TS Session Broker server, the farm name, the IP addresses to use for reconnection, and the relative weight of the server in the farm.
UPDATE (gs, 8/31/07): I realized in the original version of this post I neglected to discuss adding the necessary round-robin records to DNS to make this work (if you don't already have a 3rd party load balancer). The next step in this process is in DNS to create an A record (or AAAA record if you’re using IPv6) with the name as the farm name and the IP address as one of the servers in the farm. Repeat this process for each server-in-the-farm’s IP address.
Since NLB traditionally load balances users evenly across all servers in the farm, this ability to identify the server’s weight in the farm allows for combining dissimilar servers into a cluster. With equal weighting, the processing power of the beefiest servers impacted the smallest servers as the NLB cluster evenly distributed the load across all servers. Adding in weighting means that bigger servers get more users and lower-end servers get less.
Though this functionality isn’t nearly as robust and feature-rich as the load balancing solution provided by Citrix, in many environments it’s a “good enough” solution to ensure users get properly distributed across the servers in the cluster.
The best part of this new feature is its availability in the Standard Edition of Server 2008. In Server 2003, the TS Session Directory service was one of the few services available only in the Enterprise Edition. With Server 2008, we get this great feature in the lower-cost Standard Edition used by most of us.
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