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LSA 2: Describe Files/File Systems

When accessing files remotely, users typically connect to a shared folder over a network using specific networking protocols. To access these resources, users must provide valid credentials. If the credentials are correct, access is granted, and the files within the folder become available. However, the level of access a user has depends on their Discretionary Access Control List (DACL), which defines what actions the user is allowed to perform on the files (e.g., read, write, execute).

A file is a collection of data stored on a computer or digital device, which can contain any type of information, such as text, images, audio, video, programs, or even complex data structures.

A file system is a system that determines how data is named, stored, organized, and accessed on a storage device, such as a hard drive or solid-state drive (SSD). The operating system (OS) uses the file system to manage these files and handle various tasks, like locating files, reading from or writing to them, and organizing them in a directory structure.

There are different types of file systems, each with its own specific properties and features. The file system is typically structured in six layers:

  1. Application Programs: Software that interacts with the file system.
  2. Logical File System (LFS): Manages file naming and directory structure.
  3. File-organization Module: Deals with how files are stored and organized.
  4. Basic File System (BFS): Coordinates low-level access to the hardware.
  5. I/O Control: Manages input and output operations.
  6. Devices: The physical storage hardware.

Some common file systems include FAT (File Allocation Table), NTFS (New Technology File System), and ExFAT (Extended File Allocation Table).

File System: FAT (File Allocation Table)

The FAT file system is one of the oldest file systems, dating back to the early days of DOS (Disk Operating System). It was introduced in 1977 primarily for use with floppy disks, but was later adapted to work with hard disks and other storage devices. Initially, FAT used an 8-bit file system (FAT8), which was later expanded with different versions to support larger storage capacities.

FAT keeps track of files by using a table that maps file names to their physical locations on the disk. It does this by maintaining a file allocation table that records where each file is stored on the disk. The file system identifies the location of each file based on this table, making it easy to retrieve and store data.

FAT has been updated over time to handle larger storage capacities, with the most common versions being:

  • FAT12: Used in early floppy disks.
  • FAT16: Expanded to support larger storage devices.
  • FAT32: Further expanded, supporting even larger drives and partitions.
  • ExFAT: Designed for use with modern storage devices, offering larger file sizes and better performance for removable media.

Key Limitation: The maximum file size for FAT16 and FAT32 is 4 GB - 1 byte (exactly 4,294,967,295 bytes). This limits its use for larger files, especially for modern multimedia applications.

File System: ExFAT (Extended File Allocation Table)

ExFAT, or Extended File Allocation Table (sometimes referred to as FAT64), is a more modern and complex file system than FAT. It was specifically designed to address some of the limitations of FAT32, particularly the 4 GB file size limit. ExFAT is used primarily for removable media, such as USB drives, SD cards, and external hard drives, where large file storage is needed.

One of the biggest advantages of ExFAT over FAT32 is that it can support files larger than 4 GB and can handle storage media of any size, up to 256 TB (terabytes). This makes it an ideal choice for devices that need to store large media files, such as videos or high-resolution images.

However, ExFAT still has some of the security limitations of FAT file systems. It lacks built-in file system security features like those found in NTFS and does not include robust recovery mechanisms for damaged or corrupted files.

File System: NTFS (New Technology File System)

The NTFS file system was introduced by Microsoft in 1993 as a replacement for FAT32. It is the default file system used in modern Windows operating systems and is designed to be more reliable and feature-rich than FAT file systems.

Key features of NTFS:

  1. Compression: NTFS supports file compression, allowing files to take up less space on the disk. This can be especially useful for systems with limited storage capacity.

  2. Disk Quotas: NTFS allows administrators to set disk quotas, limiting the amount of disk space users can consume. This helps prevent individual users from consuming all available disk space on a shared system.

  3. File and Folder Security (DACLs & SACLs): NTFS allows for advanced security controls through Discretionary Access Control Lists (DACLs) and System Access Control Lists (SACLs). DACLs specify who can access or modify files, while SACLs track access attempts for auditing purposes. This provides more granular control over file and folder permissions compared to FAT systems.

  4. Reliability with Transaction-Based Logging: NTFS uses transaction-based logging (also called journaling) to keep track of changes to files. This feature helps to prevent data loss in the event of unexpected system shutdowns or crashes, making NTFS a more reliable file system.

  5. Encryption: NTFS includes support for file encryption using the Encrypting File System (EFS). This allows files to be encrypted to protect sensitive data from unauthorized access.

  6. Mounted Volumes: NTFS allows for the use of mounted volumes, which enables users to mount additional volumes (such as hard drives or network shares) as directories in the existing file system. This feature provides more flexibility in managing storage.

Summary of Key Differences

  • FAT is an older file system that works well with small storage devices but lacks modern security and performance features. It’s useful for simple, lightweight storage tasks, especially for removable media.

  • ExFAT is an improvement over FAT, offering support for larger files and storage capacities, making it ideal for external devices like USB drives and SD cards. However, it lacks the advanced security and recovery features needed for more critical data management.

  • NTFS is a highly reliable and feature-rich file system used in Windows environments. It supports security features, file compression, encryption, and logging, making it the best choice for most modern computing needs.

Each of these file systems serves different purposes based on the specific needs for storage capacity, file size, security, and data management.