SolFS in callback mode
Solid File System maintains logical filesystem structure and file data. SolFS can keep this information in a container (storage file on the local disk) or anywhere else you like. How does it do the trick?
Callback Mode is the answer. SolFS arranges all data in the storage in pages - blocks of data with fixed size. Those blocks are stored to the backend storage. In callback mode the pages are not stored but instead passed to your application, which can store the pages anywhere. For example, pages can be stored as BLOB entried in the cloud storage, thus providing you with the expandable virtual disk backed by the cloud storage.