Operating Systems File Systems and Virtualization PDF

Week 8: File Systems in OS 1. What is a File?  A file is a collection of related data stored on secondary storage.  Identified by a name and an extension (e.g.,.txt,.jpg). 2. File Structure  Determines how files are organized on a storage device.  Helps in easy retrieval and...

Week 8: File Systems in OS 1. What is a File?  A file is a collection of related data stored on secondary storage.  Identified by a name and an extension (e.g.,.txt,.jpg). 2. File Structure  Determines how files are organized on a storage device.  Helps in easy retrieval and management of files. 3. Types of Files  Ordinary Files: Contain user data (text, databases, executable programs).  Directory Files: Store names and metadata of other files.  Special Files: Represent hardware devices (e.g., disks, printers). o Character Special Files: Handle data character by character (e.g., terminals, printers). o Block Special Files: Handle data in blocks (e.g., hard drives, tapes). 4. File System Types  FAT (File Allocation Table) – Used in older Windows versions.  NTFS (New Technology File System) – Used in modern Windows with advanced security.  ext (Extended File System) – Common in Linux.  HFS/APFS – Used in macOS. 5. File Directories  Single-Level Directory: All files stored in one directory (hard to manage).  Two-Level Directory: Each user has a separate directory.  Tree-Structured Directory: Hierarchical system for better organization. 6. File Allocation Methods  Contiguous Allocation: Stores a file in a single continuous block (fast but prone to fragmentation).  Linked Allocation: Each file block points to the next one (flexible but slower).  Indexed Allocation: Uses an index table to locate file blocks (most efficient). 7. File Access Methods  Sequential Access: Reads file data in order.   Direct/Random Access: Jumps directly to specific data.  Indexed Sequential Access: Uses an index for faster lookups. 8. Free Space Management  Bit Table: A bitmap marking free and occupied blocks.  Free Block List: Keeps track of available disk blocks.  Grouping: Stores addresses of free blocks in linked lists. Week 9: OS Installation 1. Virtualization  Allows multiple virtual machines (VMs) to run on a single physical computer.  Saves costs by reducing the need for physical hardware. 2. Benefits of Virtualization  Resource efficiency: Maximizes hardware usage.  Easier management: Virtual machines are easier to maintain than physical machines.  Minimal downtime: Can switch between virtual machines if one crashes.  Faster provisioning: VMs can be set up quickly compared to physical machines. 3. Virtual Machines (VMs)  Software-based simulations of physical computers.  Each VM has its own configuration and storage.  Can take snapshots to save system states. 4. Hypervisors (VM Coordinators)  Type 1 (Bare-Metal): Runs directly on hardware (e.g., VMware ESXi).  Type 2 (Hosted): Runs inside an existing OS (e.g., VirtualBox, VMware Workstation). 5. Cloud Virtualization  IaaS (Infrastructure as a Service): Provides virtualized servers and storage.  PaaS (Platform as a Service): Provides tools for application development.  SaaS (Software as a Service): Provides cloud-based applications (e.g., Google Docs). 6. Device Management  OS manages input/output devices like keyboards, printers, and storage.  Uses device drivers to communicate with hardware.   Device Controllers: Act as intermediaries between hardware and drivers. 7. I/O Communication Methods  Polling I/O: The CPU repeatedly checks if the device is ready (inefficient).  Interrupt I/O: The device notifies the CPU when it's ready (better performance).  Direct Memory Access (DMA): Transfers data directly to memory without CPU intervention. 8. Kernel I/O Subsystem  Scheduling: Manages the order of I/O requests.  Buffering: Temporarily stores data during transfers.  Caching: Keeps frequently used data in fast memory.  Spooling: Queues data for slow devices like printers.  Error Handling: Prevents crashes due to I/O failures.