Computer Storage Fundamentals: Drives, Memory, and File Systems

Posted on Oct 27, 2025 in Technology

Storage Units and Drive Allocation

Physical and Logical Storage Devices

  • Physical Drive Storage Device Hardware: Hard Disk (HD), Reader, Recorder, Pen drive, etc.
  • Logical Drive Storage: The method used to access a physical drive.

Windows Drive Letter Allocation

Standard allocation of letters in Windows:

  • A: and B:: Floppy drives (Diskettes).
  • C:: Primary Hard Drive partition (often containing the OS).
  • D:: Subsequent Hard Disk partition or CD/DVD Reader/Writer.
  • E:: Second Reader/Writer (used for mounting images like .iso, .nrg, .cue/bin, .mds/mdf, often via virtual drive tools like Daemon Tools).
  • F:, G:, H:: Removable media (Pen drives, SD Units).
  • Network Drives: Logical drives mapped to a network path.

Additional Storage Concepts

  • File / Directory
  • Folders / Subdirectories
  • Files

Operating System Memory Management (Section 4.3)

  • Formerly: Management in real mode (memory in 3 layers).
  • Currently: Management in protected mode (linear memory).

Factors Determining Installed Memory

The amount of memory installed is determined by:

  1. Financial reasons (cost).
  2. Hardware reasons (motherboard limitations).
  3. OS software reasons (Operating System limitations).

Organization of Storage Space (Section 4.4)

The structure of a storage unit:

  • Physical Structure: Related to manufacturing material (e.g., ferrite cores, SSD). Defined by faces, tracks/side, and sectors/track.
  • Logical Structure: The data structure that allows the system to work with the storage unit.

Creating a Logical Structure

A logical structure is created through formatting (high-level formatting).

Legacy Tools (MS-DOS, Windows 95/98/ME):

  • FDISK and FORMAT (used for file systems like FAT32, NTFS).

Modern Tools (Windows XP, Vista, Proprietary):

  • Built-in proprietary tools.

Unix/Linux Tools:

  • FIPS (First Interactive Partition Splitter).

Third-Party Tools:

  • Partition Magic
  • Paragon Partition Manager
  • Partition Commander

Physical Structure of a Hard Disk (4.4.1)

  1. Sides (Heads)

    The opposing surface of each magnetic platter.

  2. Tracks (Cylinders)

    Concentric circles that divide a face. A Cylinder is formed by identical tracks across different platters.

  3. Sectors (Physical Blocks)

    The minimum amount of information read or written in one operation.

    • The sector is the fundamental allocation unit.
    • Standard Sector Size: 512 bytes (historically used for floppies and HDs) or 4096 bytes (Advanced Format).

Logical Structure of the Hard Disk (4.4.2)

The logical structure consists of:

  • Boot Sector
  • File Allocation Table (FAT)
  • Root Directory
  • Data Zone

The actual unit of space allocation used by the OS is the Cluster.

Components of the Logical Structure

  1. Boot Sector
    • Located in disk sector 0.
    • Occupies an entire sector.
    • Contains a mini-program to load the Operating System.
    • Contains the BIOS Parameter Block (BPB), which holds disk information.
  2. File Allocation Table (FAT)
    • Specifies which cluster belongs to which file.
    • Contains as many entries as there are clusters on the disk.
  3. Root Directory

    Fixed length, typically stored immediately after the FAT.

  4. Data Area

    The main area where file content is stored.

Disk Partitions (4.4.3)

Partitioning: The logical division of a hard disk into portions (partitions), each capable of containing an OS or data.

  • Primary Partitions: Up to four allowed. Designed to contain an Operating System.
  • Extended Partition: Acts as a container (often considered the fifth primary partition slot). It is divisible into multiple logical partitions.
  • Logical Partitions: Individual partitions contained within the Extended Partition.

Active Partition and Bootloaders

  • Active Partition: The partition the system looks at first during boot-up.
  • Configuration: The active partition can be configured using:
    1. Boot Drive Programs: FDISK, efdisk.
    2. Bootloader Software:
      • OS Native: Boot.ini (Windows), LILO, GRUB, SILO (Linux/Unix).
      • Commercial: GAG, BootMagic.

File Systems and Path Definition (Section 4.5)

Introduction to File Systems (FS)

  • The File System (FS) defines the structure of information stored on the storage unit.
  • The FS depends on the Operating System used.
  • The choice of FS is decided at the time of formatting.

Defining the File Path (4.5.2)

The Path defines the location of a file within the hierarchy of the file system.

The Path can be determined:

  1. Graphically (using a file explorer).
  2. Textually (using command line or URL structure).

Textual Path Examples