US Patent 9424137 Block-level backup of selected files

A block-level backup of a selected file on a source volume is done in an efficient manner by taking a snapshot copy of the source volume, and creating, mounting, and formatting a dynamically-extended backup volume, creating a sparse backup file on the backup volume, and then consolidating extents of the selected file while copying the extents at the block level from the snapshot copy of the source volume to the backup file on the backup volume. For an incremental block backup, only extents of changed blocks of the selected file are copied, and the changed blocks are identified by a modified block map of a previous snapshot copy of the source volume.