Drive Addressing and Data Organization
From Raw Hardware to Logical Blocks
1 Purpose
This document bridges the gap between the physical storage hardware discussed previously and the logical structures that an operating system uses. Before a drive can be partitioned or formatted, the system must have a fundamental way to address and organize the vast sea of storage space it represents. This reading explains that foundational layer of organization.
2 What You’ll Learn
By the end of this reading, you will be able to:
- Describe a storage drive as a raw block device composed of sectors.
- Differentiate between a drive’s physical device address and its logical storage address.
- Explain the role of Logical Block Addressing (LBA) as the standard for locating data.
- Define disk initialization and distinguish between Basic and Dynamic disk types.
This reading maps to the following program and course learning outcomes:
- Program Learning Outcomes (PLOs):
- 3. Apply terminology and numeric or system concepts: This document introduces the critical concepts of sectors, block addressing, and logical disk structures.
- Course Learning Outcomes (CLOs):
- 1. Identify hardware and basic network components: Understanding how the OS interfaces with hardware is a key part of identifying its role in the system.
This exercise develops the following skills, which align with the O*NET SOC Code 15-1232.00 for Computer User Support Specialists.
| Learning Objective | O*NET KSAs | Technologies Used |
|---|---|---|
| Explain how LBA is used to address data. | Knowledge: Computers & Electronics Abilities: Information Ordering |
LBA |
| Describe the purpose of disk initialization. | Knowledge: Computers & Electronics Skills: Reading Comprehension |
Disk Management |
3 The Drive as a Raw Block Device
When you first install a new storage drive, the operating system doesn’t see a place for files and folders. It sees a raw block device—a vast, unorganized sequence of blocks. The smallest unit of storage on any drive is called a sector.
- Sector: A fixed-size division of data on a drive. Traditionally, sectors were 512 bytes, but modern drives use 4096-byte (4KB) sectors, often referred to as Advanced Format.
Think of a brand-new drive as a book with millions of blank, unnumbered pages. Before you can create a table of contents or write anything in it, you first need a system to number the pages.
4 Addressing: How the OS Finds Data
How does the operating system ask the drive for a specific piece of data? It needs an address. There are two types of “addresses” to consider.
- Device Address: This tells the computer which device to talk to. It’s the physical path to the drive, such as “the drive connected to SATA Port 0” or “the NVMe drive in M.2 Slot 1.”
- Storage Address: This tells the drive where on its own storage medium to find the data.
Early hard drives used a physical addressing method called CHS (Cylinder-Head-Sector), which required the OS to specify the exact cylinder, head, and sector number. This was complicated and inefficient.
4.1 Logical Block Addressing (LBA)
Modern systems use Logical Block Addressing (LBA). LBA simplifies everything by presenting the drive as a simple, linear sequence of numbered blocks, starting with LBA 0 and going to the last sector on the drive.
Instead of asking for a physical location, the OS simply asks the drive’s controller for “block number 2,345,678.” The drive’s internal firmware is responsible for translating that logical block number into a physical location on the HDD platter or in the SSD flash memory. This abstraction makes the storage hardware interchangeable and far easier for the OS to manage.
5 Initialization: Preparing a Drive for Use
Before an operating system can create partitions on a new drive, the drive must be initialized. This process writes a small amount of data to the disk that defines how it will be organized. When you add a new, unformatted drive to a Windows PC, Disk Management will prompt you to initialize it.
In Windows, you are typically given two choices for initialization style:
Basic Disk: This is the standard and most common type of disk configuration. A basic disk contains primary partitions, extended partitions, and logical drives. It is the type required for all standard OS installations and data storage. The partition structure is defined by a partition table (which we will cover in the next document).
Dynamic Disk: This is a more advanced, proprietary Windows configuration. Dynamic disks can contain special volume types that a basic disk cannot, such as spanned volumes (combining space from multiple physical disks into one large volume) and striped volumes (RAID 0). While powerful, dynamic disks are less flexible and are not typically used for boot drives.
For nearly all workstation and consumer use cases, Basic Disk is the correct choice.
6 Physical vs. Logical Drives
This leads to a final important distinction:
- Physical Drive: The actual, tangible piece of hardware you install in the computer.
- Logical Drive: How the operating system sees and presents storage to the user.
A single physical drive can be divided (partitioned) into multiple logical drives. For example, one 2TB physical SSD can be partitioned to appear as a C: drive (for the OS) and a D: drive (for data). This division is purely logical and is defined in the partition table created during initialization and partitioning.
7 Reflect and Review
Now that you have reviewed this document, take a moment to reflect on your learning in your Microsoft Teams Student Notebook:
- 3 new terms you learned in this reading.
- 2 reasons why Logical Block Addressing (LBA) is an improvement over older addressing methods.
- 1 question you still have about disk initialization.
Answer these questions in your notebook to solidify your understanding:
- What is the smallest physical unit of storage on a drive called?
- In your own words, what is the main difference between a drive’s device address and its storage address (LBA)?
- When you install a new, unformatted drive in Windows for the first time, what is the first step you must perform in Disk Management before you can create a volume?
- You have one physical 1TB SSD, but in Windows File Explorer, you see a
C:drive and aD:drive. Is theD:drive a physical or a logical drive?