L26.sp11 - Distributed Systems Distributed Systems CS 425 /...

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Distributed Systems CS 425 / CSE 424 / ECE 428 Distributed Systems CS 425 / CSE 424 / ECE 428 Distributed File Systems Reading: Chapter 8 (relevant parts) 010, I . Gupta, K. Nahrtstedt, S. Mitra, N. Vaidya, M. T. Harandi, J. Hou
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File Systems File Systems A file is a collection of data with a user view (file structure) and a physical view (blocks). A directory is a file that provides a mapping from text names to internal file identifiers. File systems implement file management: Naming and locating a file Accessing a file – create, delete, open, close, read, write, append, truncate Physical allocation of a file. Security and protection of a file. A distributed file system (DFS) is a file system with distributed storage and distributed users. Files may be located remotely on servers, and accessed by multiple clients. E.g., SUN NFS and AFS DFS provides transparency of location, access, and migration of files. DFS systems use cache replicas for efficiency and fault tolerance
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Distributed File System (DFS) Requirements Distributed File System (DFS) Requirements Transparency - server-side changes should be invisible to the client-side. Access transparency : A single set of operations is provided for access to local/remote files. Location Transparency: All client processes see a uniform file name space. Migration Transparency : When files are moved from one server to another, users should not see it Performance Transparency Scaling Transparency File Replication A file may be represented by several copies for service efficiency and fault tolerance. Concurrent File Updates Changes to a file by one client should not interfere with the operation of other clients simultaneously accessing the same file.
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DFS Requirements (2) DFS Requirements (2) Concurrent File Updates One-copy update semantics: the file contents seen by all of the processes accessing or updating a given file are those they
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L26.sp11 - Distributed Systems Distributed Systems CS 425 /...

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