Understanding Hard Disk Partitions and File Systems
Hard Disk Controller
An electronic structure that controls mechanical devices.
Physical Structure of the Hard Drive
It is composed of disks or magnetic surface plates.
Partitions
Concept and Reasons for Multiple Partitions
Operating systems work with logical drives, not physical units. Each hard disk can have multiple logical drives, called partitions.
- Organizational Reasons: Allows for better file organization.
- Multiple Operating Systems: Enables installation of multiple OS on a single drive.
- Efficiency Reasons: Improves performance by separating data and system files.
Disk Structure
Each plate has two faces with concentric rings called tracks, divided into sectors.
Difference Between Directory and Partition
Partitions are fixed-size divisions of the hard drive, while directories are variable-size divisions within a partition. Partitions occupy contiguous cylinders, while directories can have scattered information. Each partition can have a different file system, but all directories within a partition share the same file system.
Types of Partitions in Windows
- Primary Partition: Can hold an operating system.
- Extended Partition: Can be further divided into logical partitions.
Partition Table
Located in the boot sector, it contains entries for each partition. An extended partition entry points to another partition table for logical partitions.
Increasing the Number of Partitions
The partition table limits the number of primary partitions to four. This can be overcome by creating an extended partition, which can hold multiple logical partitions.
Boot Sector (Master Boot Record)
Definition and Function
Stored in the partition table, it contains a small initialization program that reads the partition table and transfers control to the active partition’s boot sector, starting the operating system boot process.
Partition Boot Sector
The first sector (or sectors) of a partition contains information necessary for booting the operating system if present.
Operating System Booting
Definition and Process
Booting involves loading the operating system from the hard disk into memory. Initially, the BIOS (Basic Input/Output System) governs the computer’s operation until the OS is loaded.
File System
Definition and Purpose
A structure that enables storage, modification, and retrieval of information within a partition.
Assigning Files to Partitions
Formatting a partition creates the file system and assigns it to the partition.
File, Directory, and Link Attributes
File systems assign attributes to files, directories, and links, such as owner, permissions (read-only, read/write), creation date, file type, and size.
High-Level Formatting
Definition and Process
Creates the necessary structures for a file system, overwriting existing data but not erasing all information. It creates the boot sector and file system structures.
File Fragmentation
Causes and Explanation
Fragmentation occurs as files are created, deleted, and modified. Files are stored in contiguous free space, but if not enough space is available, they are split into fragments stored in different locations.
Defragmentation
Recommended Cases
Defragmentation is recommended when the computer is slow due to fragmented files.
Optimal Defragmentation Requirements
At least 15% of free disk space is recommended for optimal defragmentation.