We currently have a build farm of 40 build agents and running Teamcity 3.1.1.
We're in the beginning stages of validating an upgrade to teamcity 4. I'd like to test that the database upgrade goes smoothly. I can snapshot my current db and restore it as test db. I'm afraid though that if startup my teamcity 4 eap instance it will attempt "talk" to my existing buildagents.
Is this true? If so, how do you test an upgrade without interfering with existing agents?