Graph Visualization – Display informations on a group of nodes

I'm working on an application which, among other things, dynamically generates a graph representing every elements of our software architecture and their interactions. Each node represents an element of the architecture and each link represents a communication between two services.

The user can choose to group the nodes by the server on which they are hosted. The group is materialized by a big square around the nodes sharing the same server. See picture below :

Now, I'd like to display some informations on each group (like the server name, it's adress, etc ..), what would be the best way to do it ?

If I just add the infos on the rectangle, they can be hidden by the nodes. Also, some groups with only a few nodes wouldn't be big enough to display all the informations.