Designing Windows 2008 Terminal Server to run under VMWare

UKBerty used Ask the Experts™
I am designing a move of a 100 user physical server installation to a virtual environment.

At present we have 4 x Windows 2003 servers running DC/Exchange/SQL/ProgressDB/File and print etc and 6 x Windows 2000 Terminal servers. I load balance using 2X

I have good experience of VMWare and Windows 2008 which is the platform I wish to go to, but I am concerned about performance.

So my questions.....

1) We have 4Gb in the terminal servers at the moment (32 bit Windows 2000 can only see 3GB though). This means that over around 23 users the system starts to stop (which is why we have this over capacity 6x23 = 138 users). Does anyone have experience of how many users Winodws 2008 can realistically take under Terminal Server. I presume that the 64bit version with say 16GB RAM would improve this situation. Any stats anyone ?

2) Unless there's a user limit as discussed above, what's the point of virtualizing two Terminal Servers on the same physical box - You could jsut have one big terminal server ? (you could still virtualize this to make it hardware independent though).

3) If you have say 4 physical machines to virtualise the above 10 servers on would I not get a performance issue depending on which other servers end up on the same physical servers as my terminal servers. For example my DB server does certian application processes from time to time which hit the processor quite hard. If this was happening on the same physical server as one of my terminal servers then surely this would affect performance. Terminal server performance is very sensitive. Would it be better to have all virtual terminal servers on maybe 2 or 3 physical servers, which sort of brings me back to point 2.

Many thanks
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1. If using 64-bit, the reality is it will scale as long as you have the resources for it. This means there is not really a limit. Your hardware will be the limitation. It makes sense to virtualize 64-bit TSs only and not 32-bit ones as baremetal performance is not only better but much cheaper (the cost of a regular, fast server with 8GB today is so low that sometimes makes more sense to have physical TSs and not virtual ones). Also 32-bit does not scale due to the Kernel limitation (2GB) shared amongst all sessions.
Good place to read scalability tests is Project VRC. Just do a quick Google search and you will find it.

2. The point is if you have more physicals you can move these virtuals to other machines even if they are on (if using something like vMotion) so you can patch the physical host for example. If you have a big physical TS and you need to patch that physical host all your users are down. Of course if you have enough TSs and resources this would not be a huge deal as people could logoff and logon again to a different TS but still not as seamless as doing a vMotion.

3. Most virtualization solutions allow you to set 'rules' where you can say 'VM A does not run on the same physical server as VM B' and it will manage that for you.

Cláudio Rodrigues
Microsoft MVP - RDS
Citrix CTP
Markus VordererOwn Company


so to number

1) How many users a terminalserver can take depends on what the users are doing on the terminal server. by doing normal office use you can get 30 user run on a windows 2008 terminal server.

2)My limit would be 15 users per Teminal Server and add an additional Terminal Server for best performance. The Terminal Server should resist on a Raid 10 Partition with fixed Swap Settings. Also take a look at the vCPU. 4 to 8 GB Ram are ok. 2 Small Terminal Server got better performance than one big.

3) For the Reserveration of Power and CPU from the Host for theTerminal Servers build Ressource Pools. Pu in the Terminal Server and the other Server in different Pools. It is better to have the virtual Terminal Servers on different Hosts thant to put all Servers to one Host.
Make a Cluster with all hosts an put alle virtual Machines on that cluster. I would not make 2 clusters. One with DB/Exchange and so on and one with Terminal Servers. You will waist Host Ressources.

Best Regards

Top Expert 2010



Thanks - just what I needed. Many thanks also go to the VRC chaps

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