An interface between a local file system and a data store (e.g., a “write-once”store) generates and exports to the data store a “versioned” file system. The state of the local file system at a given point in time can be determined using the versioned file system. The versioned file system comprises a set of structured data representations that comprise metadata associated with actual file system data. The interface creates and exports to the data store structured data representations, which correspond to versions of the local file system, as well as the actual file system data that these structured data representations represent. A cache associated with the interface stores recently used data and metadata, as well as write data and metadata waiting to be transferred to the data store. Prior to transfer, data transformations, such as compression, encryption, and de-duplication, may be applied to the data and metadata.