Method and device for data backup

A method for storing data with a first storage system and a second storage system, wherein the second storage system is used for backing up the data from the first storage system, wherein the first storage system comprises a file system on which the data that is to be backed up is stored, with a client that monitors the first storage system, and a server that administers the second storage system, with the method comprising the following steps: checking the files on the first storage system for any changes by the client, depending on one or several events; if changes have been detected, determining a hash value in relation to the file, which hash value is structured such that the identity of the file can be determined, transmitting the hash value to the server, checking, by means of the hash value, by the server as to whether the identical file is stored on the second storage system, and if the file already exists, the file is not requested, but an annotation is made to the effect that the file is stored on the first storage system, and if the file does not exist, requesting the entire file, or parts of the file that have changed, from the first storage system, and storing the file on the second storage system, with an annotation relating to the first storage system.