The Server definition uses the WT.sv parameter, which supports a single server per page.
WT.sv
WT.sv=Name
This parameter identifies the name of the web server that served the web content. This is used for server cluster load balanced reports. The maximum length for Name is 256 bytes.
Note
The WT.sv parameter requires that the profile be set up as clustered with at least one server. This is the server that is used if an incoming hit does not explicitly have a server defined.