A shared storage distributed file system is presented that provides users and applications with transparent access to shared data stored on network attached storage devices by utilizing layering techniques to inherit file management functionality from existing file systems. The flexible membrane has a core of a first material and an outer layer of a second material having a lower adhesion to the substrate than the first material. A sleeve is carried on the shank but is removable. To obtain the map, the hot water valve is held in a substantially constant position while the chilled water valve is modulated. The controlled failure portion can be located on or in a catheter shaft, a hub assembly, andor a hub extension piece.