Chapter 19 - Distributed file systems. This chapter discusses different methods of organizing access to files and directories located in various nodes of a system, and techniques such as file caching and stateless file servers that are used to ensure good performance and reliability, respectively. | PROPRIETARY MATERIAL. © 2007 The McGraw-Hill Companies, Inc. All rights reserved. No part of this PowerPoint slide may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this PowerPoint slide, you are using it without permission. Design issues in Distributed File Systems Transparency of a file system A user need not know the location of a file in the system Location transparency: The name of a file should not reveal its location Provides user convenience Location independence: File system should be able to change the location of a file without having to change its name Enables the file system to optimize its own performance Design issues in Distributed File Systems Fault tolerance Two techniques are used to ensure that a fault does not disrupt operation of | PROPRIETARY MATERIAL. © 2007 The McGraw-Hill Companies, Inc. All rights reserved. No part of this PowerPoint slide may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this PowerPoint slide, you are using it without permission. Design issues in Distributed File Systems Transparency of a file system A user need not know the location of a file in the system Location transparency: The name of a file should not reveal its location Provides user convenience Location independence: File system should be able to change the location of a file without having to change its name Enables the file system to optimize its own performance Design issues in Distributed File Systems Fault tolerance Two techniques are used to ensure that a fault does not disrupt operation of a file system Journaling technique may be used to ensure consistency of meta data Stateless file server design eliminates the need to maintain consistency of meta data Design issues in Distributed File Systems Performance File system performance has two aspects High efficiency File caching boosts efficiency by reducing network traffic Scalability Response time should not degrade as system size grows Special scalability techniques are employed Clusters of computers Distributed locking techniques Basics of file processing in a DFS A user or process that accesses a file is called a client When the client opens a file, the DFS finds its location during name resolution DFS sets up the arrangement involving the client and file server agents This arrangement is analogous to a remote procedure call (RPC) Transparency DFS may use the following arrangement Each file is assigned a globally unique file id It is stored in the directory entry of the file DFS uses a separate data structure to hold .
