I would definitely go with references. Then I would approach the View as a two-parter. The first part is to select the customer based on the argument (under "Contextual filters"). The second part, to get the servers, would be an "attachment" type of View that uses a "Relationship" to the node reference field.

Nancy

Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.

From: Olivier BATARD
Thanks for your help, node references seems much better I agree, but
technically I can't make it work. I don't see how to setup my view
(for argument and relation) to have my result. I'll search again and
harder, that's not so easy.