Storage management policies in a virtual data storage system

1. For use in a virtual data storage system for use with a client system and a plurality of physical storage devices, the virtual data storage system including a device emulator for receiving commands and data from the client system and a storage system for storing the data as data objects to the plurality of physical storage devices in accordance with storage management policies, a method of managing multiple copies of stored data objects on multiple media types over time, the method comprising:

establishing a plurality of storage pools, each storage pool defining a group of physical storage devices that are to be treated in a uniform manner, the plurality of storage pools including a disk pool composed of a plurality of storage disks and including a tape pool composed of a plurality of storage tapes;

establishing a policy composed of a series of policy copy/delete rules that directs movement of data objects into the storage pools, wherein each rule defines a destination storage pool, a length of time that the data objects are to remain in the destination storage pool, and a data source for the data objects; and

performing copy and delete actions to manage copies of data objects among the storage pools in accordance with the policy;

wherein the series of policy copy/delete rules includes: (i) a first rule that has the disk pool as the destination storage pool, a limited retention time as the length of time that the data objects are to remain in the destination storage pool, and an external source as the data source; (ii) a second rule that has the tape pool as the destination storage pool, an unlimited retention time as the length of time that the data objects are to remain in the destination storage pool, and the disk pool as the data source;

wherein the copy action in accordance with the second rule is performed as late as possible but prior to the delete action in accordance with the first rule.

2. The method of claim 1 wherein the timing of the overall series of policy copy/delete rules is relative to initial creation of a data object.

3. The method of claim 1 wherein the timing of the overall series of policy copy/delete rules is relative to modification of a data object.

4. The method of claim 1 wherein the timing of the overall series of policy copy/delete rules is relative to access to a data object.

5. The method of claim 1 further comprising:

controlling a storage pool to control usage thresholds that cause data to be moved out of the storage pool if the storage pool becomes too full.

6. The method of claim 1 further comprising:

controlling a storage pool to control media fragmentation.

7. The method of claim 1 further comprising:

establishing a virtual tape volume in the virtual data storage system; and

associating the policy with the virtual tape volume such that data objects associated with the virtual tape volume are handled among the storage pools according to the policy.

8. The method of claim 1 further comprising:

associating the policy with a file stored to the virtual data storage system such that data objects associated with the file are handled among the storage pools according to the policy.

9. The method of claim 1 further comprising:

periodically examining a data object to assure that the data object is in conformance with the policy.

10. A virtual data storage system for use with a client system and a plurality of physical storage devices, the virtual data storage system comprising:

a device emulator for receiving commands and data from the client system;

a storage system for storing the data as data objects to the plurality of physical storage devices in accordance with storage management policies;

wherein the plurality of physical storage devices include a plurality of storage pools, each storage pool defining a group of physical storage devices that are to be treated in a uniform manner, the plurality of storage pools including a disk pool composed of a plurality of storage disks and including a tape pool composed of a plurality of storage tapes;

wherein a policy composed of a series of policy copy/delete rules directs movement of data objects into the storage pools, wherein each rule defines a destination storage pool, a length of time that the data objects are to remain in the destination storage pool, and a data source for the data objects; and

wherein the storage system performs copy and delete actions to manage copies of data objects among the storage pools in accordance with the policy;

wherein the series of policy copy/delete rules includes: (i) a first rule that has the disk pool as the destination storage pool, a limited retention time as the length of time that the data objects are to remain in the destination storage pool, and an external source as the data source; (ii) a second rule that has the tape pool as the destination storage pool, an unlimited retention time as the length of time that the data objects are to remain in the destination storage pool, and the disk pool as the data source;

wherein the copy action in accordance with the second rule is performed as late as possible but prior to the delete action in accordance with the first rule.

11. A method of operating the system of claim 10 , the method comprising:

establishing a virtual tape volume in the virtual data storage system; and

associating the policy with the virtual tape volume such that data objects associated with the virtual tape volume are handled among the storage pools according to the policy.

12. A method of operating the system of claim 10 , the method comprising:

associating the policy with a file stored to the virtual data storage system such that data objects associated with the file are handled among the storage pools according to the policy.