Abstract: File system coherency of a file system, particularly for system blocks, may be maintained by (i) duplicating and verifying the (system) blocks, (ii) writing (system) blocks as a sequence of atomic commands so that at any given time, there is a valid (system) block on a physical storage device, and/or (iii) defining the file system directory data structure with directory blocks, each of the directory blocks having at least one of a directory entry and a pointer, where updates to the directory data structure are performed atomically.

Abstract: A file system (i) permits storage capacity to be added easily, (ii) can be expanded beyond a given unit, (iii) is easy to administer and manage, (iv) permits data sharing, and (v) is able to perform effectively with very large storage capacity and client loads. State information from a newly added unit is communicated (e.g., automatically and transparently) to central administration and management operations. Configuration and control information from such operations is communicated (e.g., automatically) back down to the newly added units, as well as existing units. In this way, a file system can span both local storage devices (like disk drives) and networked computational devices transparently to clients. Such state and configuration and control information can include globally managed segments as the building blocks of the file system, and a fixed mapping of globally unique file identifiers (e.g., Inode numbers) and/or ranges thereof, to such segments.