The Defect Of Coda Distributed File System And Its Improvement

Coda is the first distributed file system which supports disconnected operation. It is developed by Carnegie Mellon University and it is still in the state of beugging and testing.The ancestor of Coda is the AFS distributed file system which is developed for the American Navy.Coda is suitable for the environment in which the network connection is not stable. The main idea of Coda is prefetching the necessary files from the server,and put them in Cache which is resident in local disk;once the client lose connection with all of the servers,it can emulate the behavior of the server and service the request of the client ,so the client can normally continue his works. The special environment of Coda brings some available problem.For example,Coda does not effectively tell user what is wrong with it.To improve the availability of Coda,the author give a new idea of translucent mechanism.For example,let the user take part in the remote management of the files in servers,because they are the experts in using the files.If the user know where the problem is,then he can know what to do nextThe user can learn some status information of the environment such as the network band and volumes status.Experienced user can solve the file conflict at client side,so the most valueable files will leave back. Further more, the user adds some new functions and some status information. In the end ,a interface program named Coda-console is developed,with which the user can control and learn the behavior of Coda,hence the availability of Coda is improved greatly.