1. A non-transitory computer storage medium, in which is stored a set of instructions that when loaded into and running in a plurality of logical computer systems, each logical computer system having memory, a processor, and a storage system, establishes a software-defined network attachable storage system comprising: a plurality of namespace servers, each namespace server operating autonomously in a distinct partition of a namespace, and a plurality of dataspace servers, each dataspace server operating in an assigned partition of a dataspace associated with the storage system, wherein: (i) in order to process a given pathname request from at least one requesting client computer, the at least one requesting client computer computes a hash value based on the given pathname and uses the hash value with a hash table to obtain the identity of a specific one of the namespace servers; (ii) the specific one of the namespace servers is configured: (a) to store persistently, in its memory, filesystem metadata associated with the distinct partition of the namespace corresponding to the specific one of the namespace servers; and (b) to use the metadata that is persistently stored in its memory in processing the given storage system pathname request from the at least one requesting client computer to return to the at least one requesting client computer a handle that identifies (i) a particular one of the dataspace servers and (ii) a particular logical block index in the dataspace; (iii) the handle is used by the at least one requesting client computer to select the particular one of the dataspace servers; and (iv) the particular one of the dataspace servers satisfies the given pathname request by accessing the particular logical block index in the dataspace identified by the handle.