ch17 - Chapter 17: Distributed-File Systems Silberschatz,...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Silberschatz, Galvin and Gagne ©2009 Chapter 17: Distributed-File Systems
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
17.2 Silberschatz, Galvin and Gagne ©2009 Chapter 17 Distributed-File Systems Background Naming and Transparency Remote File Access Stateful versus Stateless Service File Replication An Example: AFS
Background image of page 2
17.3 Silberschatz, Galvin and Gagne ©2009 Chapter Objectives To explain the naming mechanism that provides location transparency and independence To describe the various methods for accessing distributed files To contrast stateful and stateless distributed file servers To show how replication of files on different machines in a distributed file system is a useful redundancy for improving availability To introduce the Andrew file system (AFS) as an example of a distributed file system
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
17.4 Silberschatz, Galvin and Gagne ©2009 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
Background image of page 4
17.5 Silberschatz, Galvin and Gagne ©2009 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
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
17.6 Silberschatz, Galvin and Gagne ©2009 Naming and Transparency Naming – mapping between logical and physical objects Multilevel mapping – abstraction of a file that hides the details of how and where on the disk the file is actually stored A transparent DFS hides the location where in the network the file is stored For a file being replicated in several sites, the mapping returns a set of the locations of this file’s replicas; both the existence of multiple copies and their location are hidden
Background image of page 6
17.7 Silberschatz, Galvin and Gagne ©2009 Naming Structures Location transparency file name does not reveal the file’s physical storage location Location independence – file name does not need to be changed when the file’s physical storage location changes
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
17.8 Silberschatz, Galvin and Gagne ©2009 Naming Schemes — Three Main Approaches Files named by combination of their host name and local name; guarantees a unique systemwide name Attach remote directories to local directories, giving the appearance of a coherent directory tree; only previously mounted remote
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/04/2012 for the course ENG OS taught by Professor Ta during the Fall '08 term at Virginia Tech.

Page1 / 29

ch17 - Chapter 17: Distributed-File Systems Silberschatz,...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online