Patent ID: 7440966

Claim:
A method in a data processing system for managing data in a file system, the method comprising: detecting a request to modify a data block in the file system; responsive to detecting the request: writing metadata describing the data block in the file system into a snapshot image, wherein the snapshot image is updated to maintain a consistent block-level image of the file system from a point-in-time when the snapshot was created, and wherein the writing further comprises writing an in-use state of snapshot map entries for a snapshot map group to the snapshot image prior to any before-image data blocks referenced by the snapshot map group being written to the snapshot image; and copying data for the data block in the file system to the snapshot image to further update the snapshot image; and modifying the data block in the file system after copying of the data in the data block to the snapshot image has occurred, wherein the snapshot image is usable to return the file system to a state prior to modifying the data block in the file system.