Linux File System Application

For some special applied system, such as file encryption system, file compression system and file protection system, can be implemented at application layer also can be implemented at OS layer.If it implemented at application layer, obviously has some disadvantages: first, it is not transparent to other user application, user need to handle related task handly; second, it involves more communication effort between applications, makes data exchange more complicated; finally, it can hardly establish a standard interface between application modules, which affect many more difficulties on system extension and upgrade.But if bring these problems into OS layer, it will come up with some advantages: first, it is transparent to users by maintain the interface between system call and applications; second, system extension and upgrade become more easily by keep the system call interface unmodified; and more over a complicated system, putting some key functionalities into OS layer makes it possible to reduce the overall system complexity, which lead to a lower development and maintenance costs.This thesis proved that it is better to implement application in OS layer for special problem by examples of implementation of a multi-user multi-layer file system and a target compressed file system, and also provided performance data to support this.