I'd call this a VFAQ (yes, a very frequently asked question!)
A WebSphere Application Server Deployment Manager is just a Java process, can it run on the same node as a normal WebSphere Application Server, or should it run on a standalone node?
If it weren't for cost (then the world would be a different place...) then it would be a straight forward decision to place this on separate (virtual) hardware. For reasons of:
- separating the administrative process from the runtime
- it can easily be backup up
- it doesn't interfere with the application runtime (availability, memory, CPU, etc)
- patching it doesn't require taking an outage of the administrative process and a runtime server
- and the critical time that you're likely to need access to the console to troubleshoot, rollback, monitor some issue, you don't want it maxed out by some "sick" server.
So there are good reasons to separate the Deployment Manager from application nodes. In reality cost is a factor, but you should at least be aware of the above in order to mitigate the risk
Of course, this isn't needed in the same way in a test cell.