VERSIONED FILE SYSTEM WITH FAST RESTORE

摘要

A versioned file system comprises a set of structured data representations. Each structured data representation corresponds to a version, and each version comprises a tree of write-once objects. Each version in the versioned file system has associated therewith a borrow window. When it is desired to reconstruct the file system to a point in time, i.e., to perform a “restore,” it is only required to walk a single structured data representation. During a restore, metadata is pulled back from the cloud first, so users can see the existence of needed files immediately. The remainder of the data is pulled back from the cloud when the user goes to open the file. As a result, the entire file system is restored to a previous time nearly instantaneously. A fast restore is performed if an object being restored exists within a borrow window of the version from which the system is restoring.