I am just start looking at WLSDM, what is the difference of having one agent per cluster against one agent per managed server?
BTW, where I could find the resource overhead when WLSDM is used on managed servers? say, how much more heap memory it will use and how about any extra I/O it would introduced?
If you have two member cluster and these members are on different machine then install two agent. If you have 4(four) member cluster and these members on two machine (two managed server per machine). Then install two agent (same with previous). Much agent, much traffic. Same behavior, same machine… Then go for one agent.
More information is available on README: http://www.wlsdm.com/docs/README#IV.Installation
WLSDM runs on AdminServer and you should not install any application on WebLogic admin console. So, it’s run-time console, should not affect your domain. WLSDM’s AdminServer overhead is negligible; one of the least overhead in the market; because we are not injecting any code to run-time classes. Maximum overhead for the managed server (considering backend monitoring is open) is about 3%-4%.
You had better, test on your current domain; because your domain is extra ordinary and you will see that WLSDM would be one of the best solution for this domain and its infrastructure.