Abstract: In a data storage subsystem a virtual removable media server (VRMS) handles host audit requests, whether directed to a physical volume or a virtual volume physically stored in cache or in a removable physical media item. The subsystem includes a storage interface between the host and data storage facilities including a cache and a physical media library. To the host, the storage interface emulates a virtual library including a plurality of virtual media items, each containing a logical volume of data. The library may also maintain physical media items each storing one logical volume, as in a traditional library. To verify presence of a specified logical volume of the virtual library, the host sends an audit request. Responsively, the subsystem cross-references the specified logical volume in a first list to identify physical locations of underlying data. This physical location may be an address in the cache and/or a physical volume corresponding to a physical media item in the library.