A method for establishing a software-defined network attachable storage system includes establishing first and second sets of logical computer systems (which may be virtual computer systems) as namespace servers and dataspace servers respectively. Each namespace server is configured: (a) to store, in its memory, filesystem metadata, the metadata including file and directory names and information on where user data associated with the file and directory names resides, and to store in its storage system a dynamically updated copy of the filesystem metadata; and (b) to process storage system pathname requests, for a predetermined subset of the namespace, from at least one requesting client computer and to return in response to each request a handle for use by the requesting client computer; and (ii) each dataspace server is configured to store and retrieve user data in its storage system based on handles determined by the namespace servers.