1. A processor-accessible data storage system for the storage of data representing a file system with a root-accessible directory-level snapshot structure comprising: at least one computer processor; at least one storage device; a file system stored on the at least one storage device and accessible by the at least one computer processor, the file system comprising multiple metadata nodes, each metadata node comprising information about a file or directory stored on the at least one storage device; at least one executable software module executed by the at least one computer processor and configured to: receive a request to take a snapshot of a file or directory, the file or directory associated with a target metadata node; access a parent metadata node of the target metadata node, the parent metadata node comprising a reference to the target metadata node and one or more references to one or more metadata nodes associated with files or directories which are not governed by the snapshot of the file or directory; and create a copy of the parent metadata node, the copy of the parent metadata node comprising a reference to the target metadata node and no reference to any of the metadata nodes associated with files or directories which are not governed by the snapshot of the file or directory.