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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 16.1 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 16.2 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 i.e. not distinguish between local and remote files. Operating System Concepts 16.3 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 16.5 Silberschatz Galvin and Gagne .