tailieunhanh - Lecture Operating system concepts (Sixth ed) - Chapter 16: Distributed-file systems

Chapter 16 looks at the current major research and development in distributed-file systems (DFS). The purpose of a DFS is to support the same kind of sharing when the files are physically dispersed among the various sites of a distributed system. | Chapter 16 Distributed-File Systems Background Naming and Transparency Remote File Access Stateful versus Stateless Service File Replication Example Systems Operating System Concepts Silberschatz Galvin and Gagne 2002 Background Distributed file system DFS - a distributed implementation of the classical time-sharing model of a file system where multiple users share files and storage resources. A DFS manages set of dispersed storage devices Overall storage space managed by a DFS is composed of different remotely located smaller storage spaces. There is usually a correspondence between constituent storage spaces and sets of files. Operating System Concepts Silberschatz Galvin and Gagne 2002 DFS Structure Service - software entity running on one or more machines and providing a particular type of function to a priori unknown clients. Server - service software running on a single machine. Client - process that can invoke a service using a set of operations that forms its client interface. A client interface for a file service is formed by a set of primitive file operations create delete read write . Client interface of a DFS should be transparent . not distinguish between local and remote files. Operating System Concepts Silberschatz Galvin and Gagne 2002 Naming Structures Location transparency - file name does not reveal the file s physical storage location. File name still denotes a specific although hidden set of physical disk blocks. Convenient way to share data. Can expose correspondence between component units and machines. Location independence - file name does not need to be changed when the file s physical storage location changes. Better file abstraction. Promotes sharing the storage space itself. Separates the naming hierarchy form the storage-devices hierarchy. Operating System Concepts Silberschatz Galvin and Gagne .