4. A method as recited in claim 1 , wherein operating the metadata subsystem comprises allowing fixed-schema storage and allowing flexible-schema storage to be used to store metadata associated with the plurality of data objects.
4. A method as recited in claim 1 , wherein operating the metadata subsystem comprises allowing fixed-schema storage and allowing flexible-schema storage to be used to store metadata associated with the plurality of data objects. 5. A method as recited in claim 4 , wherein operating the metadata subsystem comprises using both fixed-schema storage and flexible-schema storage concurrently to store metadata associated with the plurality of data objects.