A computer-accessible storage medium storing program instructions executable to implement a method comprising: receiving user input specifying a file system operation, a first pathname, and a second pathname, wherein the first pathname comprises a character string, wherein the first pathname points to a file, wherein the file is assigned to a first storage tier based on an importance level of the file, wherein the character string includes a plurality of components, and wherein the plurality of components includes one or more directory components, a storage tier component, and a filename component; parsing the character string to extract the one or more directory components, wherein the one or more directory components specify a first directory, the first directory includes a plurality of files assigned to a first storage tier and a plurality of files assigned to a second storage tier, and wherein the second pathname includes one or more directory components specifying a second directory and a filename component specifying a second filename; parsing the character string to extract the storage tier component, wherein the storage tier component specifies the first storage tier, wherein the first storage tier specified by the storage tier component is identified by a storage tier name, and wherein the storage tier name is determined by a portion of the storage tier component following a storage tier identifier in the character string; analyzing the first pathname to determine a first filename specified by the filename component; analyzing the second pathname to determine the second directory and the second filename; performing the file system operation, wherein the file system operation operates on the first filename, the first directory, the second filename, the second directory, and the first storage tier, wherein the file is split across the first storage tier and a second storage tier, and the file is handled through a union of the first storage tier and the second storage tier as specified in the storage tier component of the character string. receiving user input specifying a file system operation, a first pathname, and a second pathname, wherein the first pathname comprises a character string, wherein the first pathname points to a file, wherein the file is assigned to a first storage tier based on an importance level of the file, wherein the character string includes a plurality of components, and wherein the plurality of components includes one or more directory components, a storage tier component, and a filename component; wherein the first pathname comprises a character string, wherein the first pathname points to a file, wherein the file is assigned to a first storage tier based on an importance level of the file, wherein the character string includes a plurality of components, and wherein the plurality of components includes one or more directory components, a storage tier component, and a filename component; parsing the character string to extract the one or more directory components, wherein the one or more directory components specify a first directory, the first directory includes a plurality of files assigned to a first storage tier and a plurality of files assigned to a second storage tier, and wherein the second pathname includes one or more directory components specifying a second directory and a filename component specifying a second filename; wherein the one or more directory components specify a first directory, the first directory includes a plurality of files assigned to a first storage tier and a plurality of files assigned to a second storage tier, and wherein the second pathname includes one or more directory components specifying a second directory and a filename component specifying a second filename; parsing the character string to extract the storage tier component, wherein the storage tier component specifies the first storage tier, wherein the first storage tier specified by the storage tier component is identified by a storage tier name, and wherein the storage tier component specifies the first storage tier, wherein the first storage tier specified by the storage tier component is identified by a storage tier name, and wherein the storage tier name is determined by a portion of the storage tier component following a storage tier identifier in the character string; analyzing the first pathname to determine a first filename specified by the filename component; analyzing the second pathname to determine the second directory and the second filename; performing the file system operation, wherein the file system operation operates on the first filename, the first directory, the second filename, the second directory, and the first storage tier, wherein the file is split across the first storage tier and a second storage tier, and the file is handled through a union of the first storage tier and the second storage tier as specified in the storage tier component of the character string. the file is split across the first storage tier and a second storage tier, and the file is handled through a union of the first storage tier and the second storage tier as specified in the storage tier component of the character string.