How to load balance Terminal Server using Windows 2003 Standard Server?

Posted on 2007-10-10
Last Modified: 2013-11-21
I need to increase my Terminal servers from one to five and would like to set up some sort of Load Balancing so that users are automatically directed to the next available server, once the first server reaches a pre-configured max connection limit - say 30 concurrent users.

I believe this is possible through network load balancing - but everything I see in Microsoft seems to refer to using a session directory server - which according to the docs is available only in W2K3 Server Enterprise and Datacenter versions. We only have Standard. Are there any other cost effective options?

Is it possible to load balance based on pre-configured number of con-current hosts?

Question by:cfgchiran
    LVL 5

    Expert Comment

    One way to do what you are stating on the cheap would be use a DNS round robin. It would generally throw users randomly to your term servers, but not in a controlled manner. Part of this would be to set your ts connection properties to limit connections to 30. That way, you never get more than 30 users on any given term server. This need you have is one of the reasons people buy Citrix. As a bonus, if you use citrix, you'll only need 4 servers to handle the load of 5 straight term server boxes. Citrix adds efficiency to the ts sessions, so you can squeeze more users on per box. Also alot of other features that can extend the usefulness of your terminal services environment.

    DNS round robin explained.

    Also, I cannot recall who, but someone makes network load balancers that accomplish the same thing
    LVL 20

    Expert Comment

    Don't confuse Load Balancing with Session Directory. All Versions of Server 2003 come with Load Balancing installed.

    You only need to enable it on each NIC that you want to use for RDP. Once installed you must configure it. There are several options when using it with TS. You just have to decide whether to use Unicast or Multicast. Both have there uses, but both have some problems. Unicast cant communicate with each of the others servers as they all have the same MAC. Multicast has a different problem as it has 2 MACs and because of such some Routers and Switches will reject the ARP. Bottom line don't use Unicast unless you have 2 NICS. If you only have a single NIC, use Multicast.

    I suggest picking up a book on TS. A very good one is: Terminal Services for Microsoft Windows Server 3003 : by Brian Madden
    LVL 31

    Accepted Solution

    I wrote and gave many presentations about load balancing on terminal services (check and - I gave a presentation about this topic at BriForum). NLB does not work that well and more than that, it is not resource based (what you should be looking for). This means if one TS has 5 users but one of these users manages to use all the CPU under a process, users will get to that server, no matter it is almost dead. A better way is to get a resource based load balancer. There are many options out there, some software based like 2X LoadBalancer. I would go for something like that.
    DNS Round Robin is ok until one server dies and you have to manually change DNS to avoid a 50% connection failure (assuming 2 TSs).

    Hope this helps,

    Cláudio Rodrigues
    Microsoft MVP
    Windows Server - Terminal Services
    LVL 20

    Expert Comment

    Thats a much better explanation than mine... Go with tsmvp's comments, as he is right on the money.

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