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.