A method of managing a file, comprising: mounting a first file system on top of a second file system; creating, by the first file system, a virtual file by partitioning a file into a plurality of segments and by linking each of the plurality of segments in an index file of the first file system, wherein the index file tracks a location and order of the plurality of segments; directing, by the first file system, the second file system to manage each of the segments of the virtual file and the index file as separate files stored in a data storage device; and characterized by : responsive to a subsequent instruction to copy the virtual file, the first file system causes the second file system to read the index file stored on the data storage device and to provide the index file to the first file system and responsively providing, with the first file system, an updated index file back to the second file system that identifies the same segments as the index file, wherein the second file system stores the updated index file on the data storage device to create a copy of the virtual file in the second file system without rewriting the separate files representing the segments of the file, further comprising performing a write request to change data of the virtual file by writing a new segment to the data storage device and linking the new segment in the index file to the other segments of the virtual file in the index file, wherein the linking the new segment comprises linking the new segment to one or more of the plurality of segment files in a position associated with a location of the changed data. mounting a first file system on top of a second file system; creating, by the first file system, a virtual file by partitioning a file into a plurality of segments and by linking each of the plurality of segments in an index file of the first file system, wherein the index file tracks a location and order of the plurality of segments; directing, by the first file system, the second file system to manage each of the segments of the virtual file and the index file as separate files stored in a data storage device; and characterized by : responsive to a subsequent instruction to copy the virtual file, the first file system causes the second file system to read the index file stored on the data storage device and to provide the index file to the first file system and responsively providing, with the first file system, an updated index file back to the second file system that identifies the same segments as the index file, wherein the second file system stores the updated index file on the data storage device to create a copy of the virtual file in the second file system without rewriting the separate files representing the segments of the file, further comprising performing a write request to change data of the virtual file by writing a new segment to the data storage device and linking the new segment in the index file to the other segments of the virtual file in the index file, wherein the linking the new segment comprises linking the new segment to one or more of the plurality of segment files in a position associated with a location of the changed data. <EOS>