Abstract: Disclosed is a computer-implemented method, system and computer program(s) for migration of a source machine instance to a target machine instance of least one heterogeneous virtual server device managed within a cloud computing environment. The method includes discovering machine images of a cloud service provider and storing results in a computer-readable catalog containing cloud metadata comprised of machine image identifiers and information discovered about the machine images. The method further includes, in response to a request for migration document in a computer-readable form that comprises a specification of a required migration target machine instance, specifying weight/priority information for components to be included in the target machine instance, where the weight information indicates weights for operations comprising component installation, component removal and component upgrade in the target machine instance.