Operating Systems I/O Management Quiz

UNIT 5: Device and File Management

• This unit covers the management of devices and files within an operating system.

Device Management in Operating Systems

• Device management is the process of implementing, operating, and maintaining devices within an operating system.
• The operating system acts as an interface between users and various devices (e.g., mouse, keyboard, printer, pen drives).
• The operating system is responsible for establishing connections between these devices and the system.
• Device drivers are used to establish connections between devices and the system.

How Device Management Works

• Device management performs tasks such as managing device operations and maintaining devices.
• It is beneficial for businesses using IT infrastructure.
• Device management helps install drivers and switches.
• Device management improves security measures.
• Device configuration simplifies IT hardware performance.
• Devices can be physical (e.g., virtual machines and switches).
• Device drivers act as an interface between the operating system and the hardware device.

Key Features of Device Management

• Device drivers interact with the device controller and execute multiple processes.
• Device drivers function similarly to system software programs to execute processes.
• A critical feature involves implementing the API.
• Device drivers are similar to software programs which allow the operating system to manage multiple devices.
• The device controller manages three registers: command, status, and data.

Operating System Responsibilities

• The operating system manages device communication through drivers.
• The operating system keeps track of devices using an input/output controller.
• It determines which process is assigned to a CPU.
• It fulfills the requests of devices to access the process.
• It connects devices to programs efficiently without errors.
• It deallocates devices when not in use.

Device Characteristics

• Accept Third-Party Cookies: Indicates whether the device accepts cookies from different domains.
• Fully Supports Flash: Indicates whether the device supports Flash.
• Is Mobile: Indicates if the device is a mobile device.
• Is Tablet: Indicates if the device is a tablet computer.
• Is Wireless Device: Indicates if the device is wireless (e.g., a mobile phone).
• Supports AJAX: Indicates if the device supports asynchronous JavaScript and XML (AJAX).
• Supports Cookies: Indicates if the device's browser supports cookies.

Functions of Device Management

• Device management starts with installing devices, drivers, and software.
• It involves configuring devices to meet business expectations.
• It tracks hardware and oversees the I/O controller.
• Key functions include monitoring device status, enforcing policies for process allocation, allocating devices, and deallocating devices efficiently.

Types of Devices

• Peripheral devices in operating systems can be categorized as dedicated, shared, or virtual.
• Dedicated devices are assigned to one job at a time until released.
• Shared devices support multiple processes concurrently via interleaving requests controlled by the Device Manager.
• Virtual devices are combinations of dedicated and shared devices—for example, a printer can become shareable via a spooling program routing requests to a disk before printing.

Input/Output Devices

• Input/output devices are responsible for input/output operations in a computer system.
• They consist of two main types: block and character devices.

Block Devices

• Store information in fixed-size blocks with unique addresses (e.g., disks).
• Allow independent read/write operations on each block.
• Disks are block-addressable devices.

Character Devices

• Deliver or accept streams of characters without focusing on block structure.
• Examples include printers and keyboards.
• Not addressable and have no seek operation.
• Various character devices exist (printers, mice, etc.).

Device Controller

• A device controller acts as a bridge between the CPU and I/O devices, handling incoming and outgoing signals.
• It uses binary and digital codes.
• I/O devices do not interact directly with the operating system; instead, they communicate through the device controller.
• Input devices generate data for the computer system (e.g., mouse, keyboard).
• Output devices accept data from the computer system (e.g., printer, display).
• I/O devices can act as both input and output.

Buffering

• Buffering enhances I/O operations.
• In an operating system, data is temporarily stored in a buffer or cache to improve access speed compared to the original data source.
• Buffers store data before it is sent or retrieved from storage devices.
• Buffering reduces access operations leading to system performance improvement.

Reasons for Buffering

• Buffering synchronizes devices with differing processing speeds.
• It manages devices with different data block sizes.
• It supports copy semantics in application I/O operations.

How Buffering Works

• The operating system allocates memory for buffers (size depending on requirements).
• Data from input devices is stored in the buffer.
• Information on buffers (e.g., data amount) helps manage operations.
• The CPU processes and retrieves data from buffers independently, accelerating device speed.
• Data in the buffer is flushed (deleted) when the operation is complete.

Functions of Buffering in OS

• Synchronization: Improves synchronization between devices and system performance.
• Smoothening: Handles different operating speeds and data block sizes to ensure smooth functioning.
• Efficient Usage: Reduces system overhead and inefficient resource usage.

Types of Buffering

• Single buffering
• Double buffering
• Circular buffering

Advantages of Buffering

• Reduced waiting time for processes accessing devices.
• Smoother I/O between devices.
• Increased system performance due to reduced calls for accessing data.
• Reduced I/O operations needed.

Disadvantages of Buffering

• Large buffers consume significant memory.
• Predicting the exact data size is challenging.
• Buffers may get occupied, leading to overflow and data corruption delays.

Disk Management in the operating system

• Disk management involves organizing and maintaining storage on a computer's hard drive.
• It involves dividing the hard drive into partitions, formatting partitions using file systems, and regularly maintaining and optimizing disk performance.

Disk Scheduling

• Disk scheduling is performed by the operating system to manage I/O requests arriving for the disk.

How Disk Scheduling Algorithms Works

• Seek Time: The time for the disk arm to move to the designated track where the data is found.
• Rotational Latency: Once on the correct track, the time taken for the desired data to rotate under the head for access.

Importance of Disk Scheduling

• Multiple I/O requests arrive simultaneously from various processes
• Disk scheduling ensures that only one request is served at a time.
• Scheduling addresses issues where requests are geographically distant, increasing disk arm movement.
• Scheduling optimizes disk access for efficiency given that hard drives are the slowest system components.

Key Terms Associated with Disk Scheduling

• Seek time: Time to position the disk arm to the designated track.
• Rotational latency: Time for the desired sector to rotate under the read/write head.
• Transfer time: Time for data transfer, dependent on the disk's rotating speed and the number of bytes.

Disk Scheduling Algorithms

• FCFS (First Come, First Served): This algorithm serves requests in the order they arrive.
• SSTF (Shortest Seek Time First): This algorithm prioritizes the request with the shortest seek time from current position.
• SCAN: Services requests in one direction until the end, then reverses direction and continues. (Elevator Algorithm).
• C-SCAN (Circular SCAN): Operates similarly to SCAN, but wraps around to the other end of the disk instead of reversing direction

Advantages/Disadvantages of Disk Scheduling Algorithms

• Detailed descriptions of advantages and disadvantages for each algorithm are provided earlier in the notes

RAID (Redundant Arrays of Independent Disks)

• RAID is a technique to use multiple disks to improve performance, data redundancy, or both, rather than using a single disk.

Why Data Redundancy?

• Data redundancy increases disk reliability, permitting data retrieval even in case of disk failures by maintaining copies of data on separate disks.

Key Evaluation Points for a RAID System

• Reliability: How many disk failures the system can handle.
• Availability: The system's uptime percentage.
• Performance: Response time and throughput.
• Capacity: The usable storage capacity.

Different RAID Levels

• RAID 0 (striping)
• RAID 1 (mirroring)
• RAID 2 (bit-level striping with dedicated parity)
• RAID 3 (byte-level striping with dedicated parity)
• RAID 4 (block-level striping with dedicated parity)
• RAID 5 (block-level striping with distributed parity)
• RAID 6 (block-level striping with two parity bits)

File System

• A file is a collection of logically related data recorded into secondary storage.
• Files are structured with names and extensions separated by periods.
• A file system is a method for files to be stored, organized, and managed on a storage device (e.g., magnetic disks, tapes, optical disks).

Advantages of File System

• Organization: Allows files to be structured into logical folders.
• Data protection: Includes features for backup, recovery, permissions, and error correction.
• Improved performance: Improves reading & writing by logical organization on disk storage.

Disadvantages of File System

• Compatibility issues: Different file systems might not be compatible with each other, making data transfer between systems difficult.
• Disk space overhead: File systems store metadata, which may reduce available space.
• Vulnerability: File systems are susceptible to data corruption, malware attacks, etc.

File System

• File structure: A file has a specific structure (e.g., text, source, object).
• File types: Different types of files are recognized by the OS.
  • Ordinary files: Contain user data (text, databases, programs).
  • Directory files: Contain lists of file names and information.
  • Special (or device) files: Represent physical devices:
    • Character devices: Handle data character by character (e.g., terminals, printers).
    • Block devices: Handle data in blocks. (e.g., disks, tapes).

File Access Mechanisms

• Sequential access: Processing of file data one record after another.
• Direct/Random access: Direct access of records through addresses.
• Indexed sequential access: Accessing files via a method using pointers in an index.

Space Allocation Techniques

• Contiguous allocation: Files occupy contiguous disk addresses to enhance efficiency.
• Linked allocation: Files consist of linked blocks, reducing external fragmentation.
• Indexed allocation: An index block containing pointers to data blocks in the file is used for flexibility.

File Sharing

• File sharing in an OS describes information exchange between users, devices, and computers.

Primary Terminology

• Folder/Directory: A container for files.
• Networking: Linking devices for resource sharing.
• IP Address: A numerical identifier for network devices.
• Protocol: Rules for communication between devices on a network.
• File Transfer Protocol (FTP): Protocol for file transfer between client and server.

Various Ways to Achieve File Sharing

• Server Message Block (SMB): Windows-based file sharing protocol.
• Network File System (NFS): Used on Unix/Linux to share files over a network..
• FTP: Used to transfer files between clients and servers across a network.
• Cloud-Based File Sharing: Using online services (e.g., Google Drive) to store and share files.

Types of File Management

• Sequential file management: Files are stored sequentially.
• Direct file management: Direct access to any file part with a file allocation table.
• Indexed file management: Employing an index to improve file access.
• File allocation table (FAT): A table used by file systems to keep track of file allocation status.
• New Technology File System (NTFS): A more advanced file system for Windows providing advanced features.
• Distributed file systems: Files stored on multiple networked devices/servers to provide transparent access in the network.

File System Reliability

• Techniques ensure integrity and availability in presence of errors or failures:
• Checksums: Computing data values and comparing them to stored values for corruption detection.
• Journaling: Logging changes before applying, enabling recovery from incomplete operations.
• Replication: Copying data to multiple locations for redundancy in failures.
• Backup: Creating copies of entire or partial file systems.

Test your knowledge on the role of device controllers and buffering in operating systems. This quiz covers key concepts such as Direct Memory Access (DMA), circular buffering, and the implications of buffering on I/O operations. Assess your understanding of how these elements enhance performance in computer systems.