Chapter 12 - Implementation of file operations. This chapter discusses the physical organization used in file systems. It starts with an overview of I/O devices and their characteristics, and discusses different RAID organizations that provide high reliability, fast access, and high data transfer rates. | 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. Input Output Control System (IOCS) The IOCS consists of two layers that provide efficient file processing and efficient device performance Access Methods layer Each access method provides efficient processing of files with a specific file organization, ., sequential file organization and direct file organization Physical IOCS layer Performs I/O operations on devices Ensures efficient device performance Physical organizations in Access methods and Physical IOCS The physical IOCS reads data from disk into buffers or disk . | 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. Input Output Control System (IOCS) The IOCS consists of two layers that provide efficient file processing and efficient device performance Access Methods layer Each access method provides efficient processing of files with a specific file organization, ., sequential file organization and direct file organization Physical IOCS layer Performs I/O operations on devices Ensures efficient device performance Physical organizations in Access methods and Physical IOCS The physical IOCS reads data from disk into buffers or disk cache/file cache maintained in memory (or writes data), ensuring high device throughput The access method moves the data between buffers or caches and the address space of the process, ensuring efficient file processing Policies and Mechanisms Policy A guiding principle for implementing a functionality (., priority-based scheduling) It invokes mechanisms to perform various actions required to implement the functionality Mechanism Specific action in implementing a functionality Layers of File system and IOCS M: Mechanism module, P: Policy module A policy module invokes mechanism modules of the same layer, which may invoke policy and mechanism modules of the lower layer Policies and mechanisms in file system and IOCS layers Model of a computer system The I/O subsystem has an independent data path to memory Devices are connected to device controllers, which are connected to the DMA; a device is identified by the pair (controller id, device id) The DMA, a device controller, and a device .
