In persistent environments (e. g., persistent OOPLs, OODBSs), twodifferent kind of physical storage- memory and disk are involved. An abstract storage level should be developed to hide physical details. The virtual object storage(VOS) proposed in this paper is such an abstract storage level on which persistent objects and transient objects can be manipulated uniformly. The author has developed the dual-copy model for the VOS implementation. And the benefits of the VOS approach for persistent OOPL design and implementation are illustrated by the experiences with XDPC+ +, a persistent OOPL based on C+ +.