Actually there is no direct way to get the information in PI Vision mentioning to which member of the collective the server is connected , we have the same topic with PI Analysis , there is no direct way so monitor the member of the collective that was used to perform calculation.
Since there is no way to have the guarantee that all the member of the collective have exactly the same set of data it is really important to make the switch of member possible by script and to make the monitoring of this connection possible !