Concepts for remote storage of data are presented. Once such concept is a system comprising: a primary storage controller; and a secondary storage controller of a remote data storage system. The primary storage controller is configured to determine a service characteristic of data storage to or data retrieval from the remote data storage system and to communicate service performance signals to the secondary storage controller based on the determined service characteristic. The secondary storage controller is configured to receive service performance signals from the primary storage controller, to compare the received service performance signals with a service requirement so as to determine a service comparison result, and to control data storage to or data retrieval from the remote data storage system based on the service comparison result.