Patent ID: 8099394

Claim:
A method of operating a data processing system, the system comprising application programs requiring persistent data storage for data files of application data, a plurality of physical storage devices each accessible via a computer network to one or more computers executing the application programs, and a broker program, wherein the method comprises: receiving, by the broker program, a request from an application program for storage of a data file of application data of the application program, the request including an expiry date set by the application program, beyond which the data file is no longer required and will be deleted; selecting, by the broker program, a first physical storage device of the plurality of physical storage devices to store the data file according to the expiry date of the data file and a state of the first physical storage device by: affirming that the expiry date of the data file occurs before a device expiry date associated with the first physical storage device; affirming that the expiry date of the data file occurs within a predetermined range of the device expiry date; and preventing, by the broker program, the data file from being deleted until the expiry date of the data file has been reached; wherein the selecting step comprises: monitoring, using the broker program, remaining storage space available on each of the storage devices, to distinguish between in-use storage devices which have had data files written thereon and empty storage devices which have not had data files written thereon; and choosing the in-use storage devices in preference over the empty storage devices.