Introduction

Partitioning in operating systems is the practice of dividing a storage device, such as a hard drive or SSD, into distinct sections or partitions. This process plays a pivotal role in organizing data, improving system management, and ensuring efficient data storage and retrieval. In this chapter, we will explore the concept of partitioning, its various types.

Partitioning

At its core, partitioning involves splitting a storage device into separate sections, each of which appears as an independent storage volume to the operating system. These partitions serve as containers for data, applications, and the operating system itself. The practice of partitioning can be seen as analogous to dividing a large room into smaller compartments for better organization and use.

Why Partition?

Partitioning offers several significant advantages:

Data Isolation: Partitioning separates data, making it easier to manage, back up, and recover. If one partition becomes corrupted or experiences issues, it is less likely to affect other partitions.

Performance Optimization: By placing the OS and frequently used files on a separate partition, you can boost system performance. This separation reduces file fragmentation and minimizes read/write conflicts.

Multi-Boot Systems: Partitioning is essential for systems running multiple operating systems. Each OS can reside on its own partition ensuring they do not interfere with one another.

Security: You can isolate sensitive or critical data on a separate partition, which can help protect it from unauthorized access or malware.

Types of Partitioning Schemes

There are several partitioning schemes, each with its own characteristics and use cases. The most common partitioning schemes are:

Master Boot Record (MBR):

MBR is one of the oldest partitioning schemes and is used on a 32-bit structure. It supports up to four primary partitions, making it suitable for smaller storage devices. However, it has limitations in terms of disk size and data integrity. MBR is typically used with BIOS-based systems and older hardware.

GUID Partition Table (GPT):

GPT is a modern partitioning scheme based on a 64-bit structure. It supports larger storage devices (beyond 2.2 terabytes), offers better data integrity features, and allows for up to 128 primary partitions. GPT is the preferred choice for newer hardware, UEFI-based systems, and larger-capacity storage devices.

Partitioning Process

Partitioning in an OS is the process of dividing storage device, such as a hard drive or SSD, into separate, logical sections called partitions. Each partition acts as an independent storage unit that the operating system recognizes as a distinct drive. Partitioning is essential for efficient data organization, data isolation, and system management. Here's a more detailed explanation of how partitioning works in an OS:

Initialization and Hardware Recognition:

When a computer boots up, the system BIOS or UEFI firmware initializes the hardware components, including storage devices. The BIOS/UEFI identifies the storage devices connected to the computer, such as hard drives, SSDs, and optical drives.

Partition Table:

The BIOS/UEFI then reads the partition table on the storage devices. The partition table is a data structure that stores information about the partitions on the device, including their size, starting and ending points, and file system type. The most common partition table types are Master Boot Record (MBR) and GUID Partition Table (GPT).

Partitioning Tools:

To create, modify, or manage partitions, users typically employ partitioning tools or utilities. These tools are part of the operating system and allow users to interact with the storage devices and partition tables. Popular partitioning tools include Disk Management in Windows, Disk Utility in macOS, and various command-line tools in Linux.

Partition Creation:

Using a partitioning tool, users can create partitions on the storage device. They specify the size of each partition and may assign a label or name for identification. The partitioning tool updates the partition table to reflect the newly created partitions.

File System Formatting:

After partition creation, each partition must be formatted with a file system that the OS can recognize and use. The file system define how data is stored, organized, and accesses on the partition. Common file systems include NTFS (Windows), ext4 (Linux).

Drive Letters or Mount Points:

In Windows, partitions are typically assigned drive letters (e.g., C:, D:, E:). In macOS and Linux, partitions are mounted to specific directories in the file system. Drive letters or mount points provide access to the partition's contents from within the OS.

Data Storage and Management:

Once partitions are created and formatted, users can start storing data on them. Each partition acts as an isolated storage space, logically separated from other partitions. Users can manage data within each partition independently, including copying, moving, and deleting files and folders.

System Booting (for OS Partition):

If a partition is designated as the OS partition, it becomes the boot partition. During system startup, the BIOS or UEFI firmware locates the boot partition, loads the bootloader, and initiates the OS boot sequence. The OS is then loaded from the boot partition into system memory, allowing the computer to operate.

Partition Table

A partition table is a crucial data structure that serves as a map or index for the organization and management of partitions on a storage device, such as a hard drive or SSD. It is an integral part of the storage device's firmware and is essential for the operating system to locate, access, and manage the various partitions on the device.

Key points to understand about partition tables:

Partition Information: A partition table contains information about the partitions on the storage device. This information includes details such as the starting and ending positions of each partition, the size of each partition, the type of file system used, and a unique identifier for each partition.

Partitioning Schemes: Partition tables are closely tied to the type of partitioning scheme being used. The two most common partitioning schemes are Master Boot Record (MBR) and the GUID Partition Table (GPT). Each of these schemes has its own way of structuring the partition table.

Master Boot Record (MBR): In a MBR partition table, the first sector of the storage device (known as the Master Boot Record) contains the partition table. MBR is a legacy partitioning scheme and has limitations in terms of the number of partitions it can support and the maximum disk size.

GUID Partition Table (GPT): GPT is a modern partitioning scheme that uses a partition table at the beginning and end of the storage device, providing redundancy for data integrity. GPT is designed to support larger devices and offers enhanced data protection.

Partition Table Maintenance: The partition table is maintained by the operating system and partitioning tools. When you create, modify, or delete partitions, the partition table is updated to reflect these changes.

Partition Table Backup: In GPT partitioning, the scheme provides redundancy by storing a backup of the partition table at the end of the storage device. This redundancy enhances data integrity and helps in case of table corruption.

Location of Partition Table

The location of the partition table depends on the partitioning scheme used for the storage device. There are two primary partitioning schemes: Master Boot Record (MBR) and GUID Partition Table (GPT). Here's where the partition table resides in each of these schemes:

Master Boot Record (MBR):

In the MBR partitioning scheme, the partition table is located in the first sector of the storage device, often referred to as the “Master Boot Record” sector. This sector is the very first sector on the storage device and is identified by the sector number 0 (cylinder 0, head 0, sector 1 in disk geometry). The MBR sector is 512 bytes in size, and the partition table consumes a portion of this space. The remaining part of the sector typically contains the bootloader and a signature that indicates the MBR is valid.

The MBR partition table in the MBR sector can store information about up to four primary partitions or three primary partitions and one extended partition, along with their characteristics, such as starting and ending sectors and partition type.

GUID Partition Table (GPT):

In the GPT partitioning scheme, the partition table is more extensive and resides at both the beginning and end of the storage device. This redundancy is designed to enhance data integrity and recovery. The GPT structure includes the following components:

• Protective MBR: Although GPT does not rely on the MBR scheme, it includes a “protective MBR” at the beginning of the storage device to prevent older systems from attempting to modify the GPT structure.
• Primary GPT Header: Located at the beginning of the storage device, this section contains essential information about the GPT structure, including the number and size of partitions.
• Partition Entries: Each partition entry provides detailed information about a specific partition, similar to the MBR scheme.
• Backup GPT Header: Located at the end of the storage device, this section is a redundant copy of the primary GPT header, further enhancing data integrity.

The GPT partition table and related components are distributed across both the beginning and end of the storage device to provide data redundancy and ensure that the GPT structure can be reconstructed in case of damage or corruption.