You may define global resource in grid page, with desired concurrent count, and set up the configuration to require that resource in general settings.

Thanks to reply.
However, we have common resource for various purpose in grid page.
If concurrent count could configure in each configuration, it would be great.
Please consider it to support even though from next version.
Thanks again.

Configuration A : We want to run 10 builds simultaneously.

Case 1) Recommend of you
Server A : 5 agents
Server B : 5 agents

If one server is shutting down, we have only 5 agents.

Case 2) Our current setting
Server A : 10 agents
Server B : 10 agents

Even if one server is shutting down, we have at least 10 agents. (failover)

However, we want to make 10 active running agents always.

I handle a similar situation by having configuration rely on two resources. One to select the host where the job runs, and one to throttle parallel jobs.

If you give more details of your situation maybe I can make suggestions.

I mean global resource, instead of node resource. Without global and node resource, the build can run on all agents concurrenty (20 concurrently if you have 20 agents), and you can limit it to 10 by defining a global resource with 10 concurrency.

Thanks to reply, I found the feature which robin told. Thanks.

Thanks to reply again, I found the feature which you told. Thanks.