Learning Objectives

By the end of this chapter, you will be able to:

  • Define secondary storage and its purpose.
  • Describe how a Hard Disk Drive (HDD) works.
  • Describe how a Solid-State Drive (SSD) works and its advantages over an HDD.
  • Identify common types of optical storage.

Secondary Storage Devices

Secondary storage refers to the non-volatile devices and media used for long-term storage of data and programs. Unlike primary memory (RAM), secondary storage retains its data even when the computer is turned off.

1. Hard Disk Drives (HDD)

For decades, the Hard Disk Drive was the primary form of secondary storage in computers.

  • How it Works: An HDD is a mechanical device that stores data on rapidly rotating platters with magnetic surfaces. A read/write head on a mechanical arm moves across the platters to read and write data.
  • Characteristics: HDDs offer very large storage capacities at a low cost per gigabyte. However, because they have moving parts, they are slower, less durable, and consume more power than newer technologies.

2. Solid-State Drives (SSD)

Solid-State Drives are now the standard for primary storage in modern laptops and desktops.

  • How it Works: An SSD has no moving parts. It stores data on interconnected flash-memory chips.
  • Characteristics: Because they have no moving parts, SSDs are significantly faster, more durable, quieter, and more power-efficient than HDDs. However, they are more expensive per gigabyte.

3. Optical Storage

Optical storage devices use a laser to read and write data on a spinning disc.

  • How it Works: A laser beam creates tiny pits in the surface of the disc to represent data. Another laser reads these pits.
  • Characteristics: Optical discs are portable and inexpensive, but they have a much smaller capacity and are much slower than HDDs and SSDs. They are becoming less common in modern computers.
  • Examples: Compact Discs (CDs), Digital Versatile Discs (DVDs), and Blu-ray Discs.

Summary

Secondary storage devices provide the long-term, non-volatile memory for a computer. The main types are mechanical Hard Disk Drives (HDDs), which offer large capacity at a low cost, and Solid-State Drives (SSDs), which have no moving parts and are much faster and more durable. While once common, optical drives like CD/DVD drives are now largely being replaced by faster and more convenient storage solutions.

Key Takeaways

  • Secondary storage is non-volatile and used for long-term data storage.
  • HDDs are mechanical drives with high capacity and low cost.
  • SSDs are flash-based drives that are much faster and more durable than HDDs.
  • Optical drives (CD, DVD, Blu-ray) are a slower, portable storage format.

Discussion Questions

  1. What are the main advantages of an SSD over an HDD?
  2. If you were buying a new computer today, would you choose one with an HDD or an SSD? Why?
  3. Why are optical drives becoming less common in modern computers?