A server system comprising a physically separate storage area for each of a plurality of respective parties including a first and second party, and a manager function for managing the storage. E.g. some of the storage areas may be in separate server units or at separate geographic locations. Each of at least some of the storage areas stores a primary instance of one or more data resources of the respective party. The manager function is configured so as, in response to the second party forming a relationship with one of the resources of the first party, establish a secondary copy of said one of the resources of the first party in the respective storage area of the second party. Further, when the primary instance is updated with a change, the manager function automatically propagates the change in the primary instance to the secondary copy in the second party's storage area.