Lecture Operating systems: A concept-based approach (2/e): Chapter 7 - Dhananjay M. Dhamdhere

PROPRIETARY MATERIAL. © 2007 The McGraw­Hill 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 McGraw­Hill for their individual course preparation. If you are a student using this PowerPoint slide, you are using it without permission. File Systems Dhamdhere: Operating Systems— Copyright © 2008 Goals of a File system • Convenient and fast access to files – Different file organizations to suit different user requirements • Reliable storage of files – Prevents damage due to crashes, etc. • Controlled sharing of files – Unauthorized persons should not be able to access files • …. also ensure efficient use of I/O devices – We discuss this aspect in Chapter 12 File Systems Dhamdhere: Operating Systems— Copyright © 2008 Structure of a File system • A file system is structured into a hierarchy of layers – File system layer * Deals with files as objects Creates files, allocates disk space to them Implements file sharing and prevents unauthorized access Prevents damage due to crashes – Input-Output Control System (IOCS) layer * Implements file system operations, ensuring Efficient access to records in files Efficient operation of I/O devices File Systems Dhamdhere: Operating Systems— Copyright © 2008 File system and IOCS layers • Each layer contains policy and mechanism modules • A mechanism module invokes modules of the lower layer File Systems Dhamdhere: Operating Systems— Copyright © 2008 File system • A Directory – Groups a set of files * It contains an entry for each of these files * The entry contains information useful for accessing the file – Users have different directories * Helps to separate files of different users * Provides file naming freedom – Directories are organized in a hierarchical structure * Permits a user to organize her files logically, e.g., according to activities File Systems Dhamdhere: Operating Systems— Copyright © 2008 ... - tailieumienphi.vn