Computer Science
File Systems
File systems are a way of organizing and storing data on a computer's hard drive. They provide a hierarchical structure for files and directories, and allow for efficient access and retrieval of data. Different file systems have different features and limitations, and can be optimized for different types of data storage and retrieval.
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10 Key excerpts on "File Systems"
eBook - PDF- Abraham Silberschatz, Peter B. Galvin, Greg Gagne(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
It provides the mechanism for on-line storage of and access to both data and programs of the operating system and all the users of the computer system. The file system consists of two distinct parts: a collection of files, each storing related data, and a directory structure, which organizes and provides information about all the files in the system. File Systems live on devices, which we described in the preceding chapter and will continue to discuss in the following one. In this chapter, we consider the various aspects of files and the major directory structures. We also discuss the semantics of sharing files among multiple processes, users, and computers. Finally, we discuss ways to handle file protection, necessary when we have multiple users and we want to control who may access files and how files may be accessed. CHAPTER OBJECTIVES • To explain the function of File Systems. • To describe the interfaces to File Systems. • To discuss file-system design tradeoffs, including access methods, file sharing, file locking, and directory structures. • To explore file-system protection. 10.1 File Concept Computers can store information on various storage media, such as magnetic disks, magnetic tapes, and optical disks. So that the computer system will be convenient to use, the operating system provides a uniform logical view of stored information. The operating system abstracts from the physical properties of its storage devices to define a logical storage unit, the file. Files are mapped by the operating system onto physical devices. These storage devices are usually nonvolatile, so the contents are persistent between system reboots. 455 456 Chapter 10 File System A file is a named collection of related information that is recorded on secondary storage. From a user’s perspective, a file is the smallest allotment of logical secondary storage; that is, data cannot be written to secondary storage unless they are within a file.
eBook - PDF- Jocelyn O. Padallan(Author)
- 2023(Publication Date)
- Arcler Press(Publisher)
The data is conveniently extracted and distinguished by dividing it into pieces and giving every component a name. Every group of data is referred to as a “file,” after the manner a paper-based information management system is referred to. A “file system” is the design and logic rules employed to organize sets of data and their names. There are numerous types of File Systems. Each one has a unique structure and logic, as well as speed, adaptability, security, size, and other characteristics. Some File Systems are intended to be used just for specific applications. The ISO 9660 file system, for instance, is developed exclusively for optical discs. File Systems can be employed on a variety of storage devices that utilize various types of media. Hard disk drives are still important storage devices in 2018 and are expected to be so for the foreseeable future. SSDs, magnetic tapes, and optical discs are some of the other types of media that are used. In other circumstances, such as with tmpfs, the main memory (RAM) of the computer is used to establish a temporary file system for relatively brief use. Some File Systems are utilized on local data storage devices, while others enable file access through a network protocol. Other File Systems are “virtual,” which means that the given “files” (known as virtual files) are computed on demand (like procfs and sysfs) or are just a mapping into another file system exploited as a backing store. The file system controls access to both the information of files and their metadata. It is in charge of organizing storage space; dependability, efficiency, and tuning in relation to the actual store medium are all significant design factors (Fröhlich and Wanner, 2008). File System 187 Prior to the invention of computers, the phrase file system referred to a method of storing and accessing paper records. By the 60s, the phrase had been extended to include automated filing in addition to its original meaning.
eBook - PDF- Abraham Silberschatz, Peter B. Galvin, Greg Gagne(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
Part Six File System A file is a collection of related information defined by its creator. Files are mapped by the operating system onto physical mass-storage devices. A file system describes how files are mapped onto physical devices, as well as how they are accessed and manipulated by both users and programs. Accessing physical storage can often be slow, so File Systems must be designed for efficient access. Other requirements may be important as well, including providing support for file sharing and remote access to files. 13 C H A P T E R File-System Interface For most users, the file system is the most visible aspect of a general-purpose operating system. It provides the mechanism for on-line storage of and access to both data and programs of the operating system and all the users of the computer system. The file system consists of two distinct parts: a collection of files, each storing related data, and a directory structure, which organizes and provides information about all the files in the system. Most File Systems live on storage devices, which we described in Chapter 11 and will continue to discuss in the next chapter. In this chapter, we consider the various aspects of files and the major directory structures. We also discuss the semantics of sharing files among multiple processes, users, and computers. Finally, we discuss ways to handle file protection, necessary when we have multiple users and want to control who may access files and how files may be accessed. CHAPTER OBJECTIVES • Explain the function of File Systems. • Describe the interfaces to File Systems. • Discuss file-system design tradeoffs, including access methods, file shar- ing, file locking, and directory structures. • Explore file-system protection. 13.1 File Concept Computers can store information on various storage media, such as NVM devices, HDDs, magnetic tapes, and optical disks.
eBook - PDF- Palmer, Greg Tomsho(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
Hierarchical Structure The overall purpose of a file system is to create a structure for filing data. The analogy that is typically used for a file system is that of file cabinets, file drawers, and file folders. For 146 Chapter 4 File Systems Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 example, the computer could be considered the file cabinet and the disk drives the drawers. Within each drawer (drive), information is organized into hanging folders, manila folders, and individual documents (files), as shown in Figure 4-1. Computer Disk drives Folders Subfolders Files Figure 4-1 A file system metaphor A file is a set of data that is grouped in some logical manner, assigned a name, and stored on the disk. As the file is stored, the file system records where the file is located on the disk so that it has a way to later retrieve that file. Whenever the file is needed, the operating system is given the filename, and it retrieves the data in the file from the disk. The data contained in files can be text, images, music and sounds, video, or Web pages. But no matter what kind of data is stored in the file system, it must be converted into digital format — a series of 1s and 0s — that the computer understands. The operating system, along with the applications you use for word processing, graphics, and so on, performs this func-tion of converting data into digital format for the computer, and back into the end-user format as text or pictures, for example. Moreover, there must be a way to write digital information to disk, track it, update it when necessary, and call it back when the user or a user-controlled program wants it. To achieve all this, the operating system typically groups file data in some logical way, creates a record 4 Understanding File System Functions 147 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
eBook - PDF- Greg Tomsho(Author)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
file, the Excel application is loaded into memory and then opens the file. If a user creates a file or changes an existing file and wants to save it, the application calls the file system to store the new or changed file on the disk. Most users of an OS interact with the file system by using a file manager program, such as File Explorer in Windows or Files in the GNOME desktop in Linux. As a future computer or network professional, you need to have a deeper understanding of how a file system works so that you can make informed choices when you need to install a file system or troubleshoot file system-related problems. Hierarchical Structure The overall purpose of a file system is to create a structure for filing data. The analogy that is typically used for a file system is that of file cabinets, file drawers, and file folders. For example, the computer could be considered the file cabinet and the disk drives the drawers. Within each drawer (drive), information is organized into hanging folders, manila folders, and individual documents (files), as shown in Figure 4-1. Figure 4-1 A file system metaphor Computer Disk drives Directories Subdirectories Files MODULE 4 File Systems 141 Copyright 2021 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. A file is a set of data that is grouped in some logical manner, assigned a name, and stored on the disk. As the file is stored, the file system records where the file is located on the disk so that it has a way to later retrieve that file.
eBook - ePubDemystifying Embedded Systems Middleware
Understanding File Systems, Databases, Virtual Machines, Networking and More!
- Tammy Noergaard(Author)
- 2010(Publication Date)
- Newnes(Publisher)
Figure 5.2 ). In short, a file system needs to support the structure of the data within a file in order for that particular file to be compatible with the file system.The first steps to understanding the fundamentals and ultimately any file system implementation are:Figure 5.2 Raw Files and File SystemsStep 1. Understand what the purpose of the file system is within the system, and simply keep this in mind regardless of how complex a particular file system implementation is. As introduced at the start of this chapter, the purpose of a file system is to manage data stored on some type of storage medium located within the embedded device and/or some remotely accessible storage medium.Step 2. Understand the APIs that are provided by a file system in support of a file system’s inherent purpose. These APIs can, of course, differ from file system to file system – but in general include some combination of:• Naming and creating files • Configuring files • Removing files • Opening and closing files • Writing to and reading from files• Creating and configuring directories for groups of files• Removing directories • Reading directories • Additional/extended functions • File system creation, mounting, and unmounting • Symbolic, hard, and/or dynamic links • Journaling/atomic transactionsStep 3. Using the Embedded Systems Model, define and understand all required architecture components that underlie the file system, including:Step 3.1. Know your file system-specific standards (see Chapter 3 ).Step 3.2. Understanding the hardware (see Chapter 2
eBook - PDF- Greg Tomsho(Author)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
In most File Systems, folders or directories don’t contain the data that makes up the actual file; they contain information about the file along with a pointer to the file’s location on the disk. Information for each file is usually called a directory entry . • Data storage method —Space on hard disks is divided into one or more partitions with each partition containing its own file system. A partition is typically divided into 512 byte sectors. The file system groups one or more sectors into blocks or clusters, which are used as the basic unit of storage for file data. These blocks are indexed so that the file data they contain can be retrieved easily. A single file can occupy from one to many thousands of blocks. File Systems vary in the methods used for indexing and managing these blocks, which affect the efficiency and reliability of data storage and retrieval. • Metadata —Metadata is information about a file beyond its name and the data it contains. This information is generally stored by the directory or folder with the file’s name or in a data structure the directory entry points to. Metadata can include time stamps indicating when a file was created, last changed, and last accessed; descriptive information about the file that can be used in searches; file attributes; and access control lists. CHAPTER 4 Configuring Storage and File Systems 118 • Attributes —Attributes are usually on/off settings, such as Read Only, Hidden, Compressed, and so forth. File Systems differ in the attributes that can be applied to files and folders. • Access control lists (ACLs) —ACLs determine who can access a file or folder and what can be done with the file (read, write, delete, and so on). File Systems vary in whether and how each component is used. Generally, more advanced File Systems have flexible file naming rules, an efficient method of managing data storage, a considerable amount of metadata, advanced attributes, and ACLs.
eBook - PDFThe Architecture of Computer Hardware, Systems Software, and Networking
An Information Technology Approach
- Irv Englander, Wilson Wong(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
We begin this chapter by reviewing the differences between the logical, or user, view of a file and the physical requirements of its storage and retrieval. Next, we show how the file management system accomplishes its mission of providing a logical file view to the user and the user’s programs. You will see how logical file system requests are mapped to physi- cal files. You will see how files are physically stored and retrieved, and how the logical file commands that you issue to the operating system are implemented. You will see some of the trade-offs that must be made as a result of specific user and program requirements and the limitations of different file storage methods. You will understand how a directory system works and read about some of the different methods that are used by File Systems to keep track of and locate files and directories. You will see how the file manager finds and allocates space for files, and how it reclaims and keeps track of space vacated when a file is moved or deleted. We hope that, as a result of the discussion in this chapter, you will be able to use and man- age computer File Systems more effectively. 18.1 The Logical and Physical View of Files Whether on computer or paper, a file is an organized collection of data. The organization of the file depends on the use of the data and is determined by the program or user who created the file. Similarly, the meaning of the data in the file is established by the program or user. A computer file may be as simple as a single data stream that represents an entire program to be loaded at one time, or a collection of text data read sequentially, or a video; or as com- plex as a database made up of individual records, each with many fields and subfields, to be retrieved one or a few records at a time in some random order. Nearly all data in the computer is stored and retrieved as files.
eBook - PDFComputer Forensics
Evidence Collection and Management
- Robert C. Newman(Author)
- 2007(Publication Date)
- Auerbach Publications(Publisher)
189 Chapter 9 Computer Systems Disk and File Structures Chapter Objecties Identify the various components of a hard drive and the structure of disk media Learn the differences among the numerous disk drive interfaces and functions Become familiar with the Windows, Macintosh, and Linux file structures Learn the definitions of numerous terms relating to file and storage structures Identify forensic tools used to identify and retrieve evidence from Windows, Macintosh, and Linux systems Introduction This chapter provides an overview of computer disk drives and how data is stored and managed on Microsoft, Macintosh, and Linux systems. An understanding of the File Systems and operating systems (OSs) are required in order to identify and recover latent evidence from these systems. It is essential that the computer forensic examiner understand the operation of these OSs to avoid damaging or destroying valuable evidence. Start-up and shut-down processes of the File Systems must also be understood. n n n n n 190 n Computer Forensics: Evidence Collection and Management Technical knowledge is required concerning the process of accessing and modi-fying system settings and options. A collection of OS manuals is required for each brand of computer system. A thorough understanding of disk drive operations, components, and configu-rations are required to successfully identify and retrieve digital data evidence. A number of software and hardware tools are used in these recovery activities. Forensic examination of disk drives and File Systems requires a considerable amount of education and practical experience. This type of function would be part of a computer forensic lab environment, and would be in the domain of a digital forensic examiner. A. Disk Drie Oeriew The hard disk drive is the primary storage location where data is permanently stored. Figure 9.1 provides a physical illustration of a hard disk drive.
eBook - PDF- Ann McHoes, , Ida M. Flynn, , Ann McHoes, Ida M. Flynn(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
Finally, the File Manager deallocates a file by updating the file tables and rewriting the file (if revised) to the secondary storage device. Any processes waiting to access the file are then notified of its availability. File Management in the Cloud How does cloud storage of files change the fundamental concepts of file management? The short answer is: it doesn’t. Before the cloud existed, the File Manager had to main-tain many files housed on the computer, including those that contained programs, data, and system instructions. Now, with cloud storage, many of these can now be stored on devices located in another part of the world and remain accessible via the Internet. Notable exceptions are the system files, often hidden from the user, that instruct the device on how to power-on and perform boot-up operations. All of the files stored on the cloud are managed using concepts that are identical to those described in this chapter. That is, our local device’s operating system cooperates with the far-off operating system to perform the same services we would expect if the file was stored on our built-in disk drive. In the end, the entire system, with all of its integrated operating systems, must be prepared to store each file in a way that allows all users to readily and accurately store, modify, and retrieve it. Definitions Before we continue, let’s take a minute to define some basic file elements, illustrated in Figure 8.1, that relate to our understanding of file structure. Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 258 Chapter 8 | File Management A field is a group of related bytes that can be identified by the user with a name, type, and size. A record is a group of related fields. A file is a group of related records that contains information to be used by specific application programs to generate reports.
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