Distributed file systems.

Distributed file systems launched in the 1970s, the possibility of merging into a single computer network has revolutionized the computer industry. This possibility was first to the division accessing files between computers. The initial achievements in this area have been limited to copy entire files from one machine to another. An example is the program UNIX-to-UNIX copy (uucp) and File Transfer Protocol (ftp). But they did not allow even close to access to files on the remote machine, in its capacity reminiscent access to the files on the disk. Only in the mid-1980s, several distributed file systems, which provide transparent access to network files. These were the Network File System (NFS), Sun Microsystems (1985), Remote File Sharing system (RFS) AT & T (1986) and the Andrew File System (AFS), Carnegie Mellon University (1995). These three systems sharply differed on the objectives of the development, architecture and semantics, but they are all trying to solve the same basic problem. The RFS is in almost all systems based on UNIX System V. Develop ASF moved Transarc Corporation, in which it was developed and turned into a Distributed File System (DFS), a distributed computing environment komponennt DSE (Distributed Computing Environment) Open Software Foundation. But most have been NFS, which is supported on all UNIX and many did not UNIX systems.

Common characteristics of distributed file systems.

traditional centralized file system allows multiple users working on one system to share access to files stored locally on your machine. Distributed file system expands the capabilities, allowing shared access to files to users on different machines that form through the network. The distributed file system based on client / server model. In this case, the client is a machine that appeals to a file, and under-server machine that stores files and providing access to them. Some systems require that clients and servers have different machines, while others admit to one machine and worked as a customer and as a server. It is important to note the distinction between distributed file systems and distributed operating systems. Distributed operating system such as V or Amoeba, the user looks for a centralized operating system, but also works on several machines. It can be a file system, shared by all machines system. In contrast, a distributed file system is a software layer, which manages the connection between traditional operating systems and file systems. This layer of software integrates with the operating system maschin-hostov network and provides services for distributed file access to systems that are central nucleus. Distributed file systems have a number of important properties. Every system may have all or part of these properties. This is precisely the basis for the comparison of different architectures among themselves. Network transparency - Clients should be able to access files using the same operation, and that access to local files. Transparency of-Filename should not determine its location in the network. Independence of-filename can be changed with the change of its physical metoraspolozheniya. Mobility user-Users should be able to access shared files from any network node. crash - The system should continue to operate under separate component failure (server or network segment). However, this can lead to performance degradation or eliminate access to some of the file system. Scalability - The system must be able to scale in the event of an increase in workload. Furthermore, it should be possible to gradually increase the system by adding individual components. Mobility-files should be possible to move files from one location to another for a working system.