Computer Storage & File System Essentials

Data Storage Components

Data storage refers to devices like hard disks, CD-ROMs, floppy disks, and USB drives.

Directory

A directory is an area within a storage unit used for organizing and storing files, as well as other directories or subdirectories.

Subdirectories

A subdirectory is a directory located within another directory, used for further organization of files.

File

A file is the fundamental unit of information storage.

Memory Management Modes

Real Mode Memory Management

Real Mode managed memory using three distinct layers for different functions, typically found in operating systems like Windows 9x or ME.

Protected Mode Memory Management

Protected Mode manages memory as a flat, single address space, common in operating systems such as Windows NT (including 2000, XP, Vista) or Linux.

Disk Structures

Physical Disk Structure

The physical structure of a disk is established during manufacturing, defining the number of faces, tracks per side, and disk sectors.

Logical Disk Structure

The logical structure is created by the user when formatting or reformatting a disk.

Hard Drive Physical Structure Components

• Faces: The platters where data is stored.
• Tracks: Concentric circles on each face where data is recorded.
• Sectors: The smallest addressable unit of data that can be read or written in a single operation.

Hard Drive Logical Structure Components

• Boot Sector: Contains a table with essential disk information.
• File Allocation Table (FAT): Organizes information about files within the data area.
• Root Directory: The primary directory entry zone created on the disk.
• User Data Area: The largest area of the disk, where user files are stored.

Disk Partitions

Primary Partition

A primary partition is a necessary disk space to begin using the storage unit.

Extended Partition

An extended partition is used to contain multiple logical drives or partitions within it.

Logical Partition

A logical partition occupies a portion or all of an extended partition. It is formatted with a specific file system and assigned a drive letter.

File Systems and Paths

File System

A file system structures the information stored on a storage unit.

File Path

A file path specifies the precise location of a file or directory, represented by a string of text.

Absolute Path

An absolute path identifies files and directories uniquely, without needing to consider the current drive or active directory.

Relative Path

A relative path describes the route from the current working directory down the hierarchy to the desired directory or file. Its usage requires consideration of both the current directory and the active drive.

Types of File Systems

Disk File Systems

Disk file systems are designed exclusively for storing files on a disk drive directly connected to a computer. Examples include:

• Unix/Linux: (e.g., ext4, XFS, UFS)
• Microsoft: (e.g., FAT, NTFS)
• Sun Microsystems: (e.g., ZFS)

Network File Systems

Network file systems allow access to files over a network. Examples include distributed and parallel file systems.

Special Purpose File Systems

Special purpose file systems do not fit into either the network or disk categories. Examples include CDFS (CD-ROM File System), DEVFS (Device File System), and SWAP (Swap Space File System).

Common File Systems by Operating System

• Windows 9x: FAT
• Modern Windows: FAT, NTFS, WinFS
• Linux: UFS (among others like ext4, XFS)
• OS/2: HPFS
• Macintosh: HFS/HFS+ (Hierarchical File System / HFS Plus)
• NetWare: NSS (Novell Storage Services)