3. The method of claim 1 , further comprising: maintaining a persistent, transactionally recoverable structure that stores the virtual-index-epoch map.
3. The method of claim 1 , further comprising: maintaining a persistent, transactionally recoverable structure that stores the virtual-index-epoch map. 4. The method of claim 3 , further comprising: dynamically maintaining the virtual-index-epoch map to accommodate changes in the system capacity, modeled performance of a physical partition, and actual performance of a physical partition.