Terminal Server Farm balancing with down server

[corey.taylor]

I have an 11501 that is balancing connections between my 10 terminal servers.

We are using roundrobin because we were told by TAC that leastconn and ACA do not work well with terminal server environment.

The problem is that whenever a server goes down and comes back up that server is not first inline for people reconnecting. I need help finding a way, once the down server comes back online, to make this server have a higher weight until its connections are about equal to what the other server loads are.

Any help would be greatly appreciated.

[seilsz]

You will need to use the leastconn method to accomplish this behavior.

I would be interested to hear anyone's experience with Terminal Server that would cause them to suggest not to use leastconn.

~Zach

[corey.taylor]

TAC recommended against leastconn. Leastconn in a terminal server environment does not work to well, which we experienced first hand.

The reason being, and the tac engineer had seen this before as well, that when a term server session comes in those first few packets are very small. So based on the leastconn algorithm that the CSS uses it was seing packets come back so fast that it assumed the server was not loaded heavily. Even if the server had a very heavy load and there were others who had no load.

We saw this first hand with the first servers in our config getting a majority of connections and the ones towards the end getting nothing.

[jfoerster]

Hi,

in my pinion balance leastconn should the job as it only counts the number of connections see :

http://www.cisco.com/en/US/customer/products/hw/contnetw/ps792/products_configuration_guide_chapter09186a008029c621.html#wp1038118:

balance leastconn - Least connection algorithm. This balance method chooses a running service that has the fewest number of connections.

We do not recommend that you use UDP content rules with the balance leastconn load-balancing algorithm. The service connection counters do not increment and remain at 0 because UDP is a connectionless protocol. Because the counters remain at 0, the CSS will give inconsistent results.

So if your terminal service is a running via UDP you are having a problem but in any other case it should do the job from the description given above.

The balance aca will fail due to the fact that the first and keepalive is very fast and so it can not determin the real load what you already found out.

Which method did you use balance aca or balance leastconn?

Cheers,

Joerg