Unit 3.5
A Guide to Computer Storage Devices
IT 231: IT and Application
🎯 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.
- ✅ Identify common types of optical storage.
🔍 What is Secondary Storage?
Definition: Non-volatile devices and media used for long-term storage of data and programs.
Unlike primary memory (RAM), it retains data even when the power is off.
Think of it as the computer's filing cabinet or library, where all your files, applications, and the operating system are kept permanently.
1. Hard Disk Drives (HDD)
The traditional workhorse of computer storage for decades.
How it Works ⚙️
- A mechanical device with moving parts.
- Stores data on rapidly rotating magnetic platters.
- A read/write head on a mechanical arm moves to access data.
Characteristics
- ✅ Very large storage capacities (Terabytes).
- ✅ Low cost per gigabyte.
- ❌ Slower due to physical movement.
- ❌ Less durable & consumes more power.
2. Solid-State Drives (SSD)
The modern standard for fast, responsive computing.
How it Works ⚡
- No moving parts!
- Uses interconnected flash-memory chips to store data electronically.
- Like a very large, very fast USB flash drive.
Characteristics
- ✅ Significantly faster than HDDs.
- ✅ More durable, quieter, and power-efficient.
- ❌ More expensive per gigabyte.
📊 HDD vs. SSD: The Showdown
Hard Disk Drive (HDD)
- Mechanical Parts
- Slower Speed
- Lower Cost per GB
- Less Durable
- Best for: Mass storage, backups, large media files.
Solid-State Drive (SSD)
- No Moving Parts
- Blazing Fast Speed ⚡
- Higher Cost per GB
- More Durable
- Best for: Operating System, frequently used applications.
Pro Tip: Many modern systems use both! An SSD for the OS and apps, and an HDD for data.
Practical Application: Buying a Laptop in Nepal
Imagine you're at a computer shop in Putalisadak, Kathmandu. Which drive do you choose?
Scenario 1: University Student
- Needs: Fast boot-up for classes, quick application loading for assignments.
- Context: Laptops get carried around, risking bumps. Power stability can be a concern.
- Best Choice: An SSD is essential. Its speed and durability (no moving parts) make it perfect for student life.
Scenario 2: Media Professional
- Needs: Storing large video files and photo libraries.
- Context: Budget is a factor, but large capacity is non-negotiable.
- Best Choice: A hybrid setup. A 256GB/512GB SSD for the OS and editing software, plus a 1TB+ HDD for storing raw footage and archives.
3. Optical Storage 💿
Uses a laser to read and write data on a spinning disc by creating tiny pits on its surface.
CD
Compact Disc (~700 MB)
DVD
Digital Versatile Disc (~4.7 GB)
Blu-ray
Blu-ray Disc (~25 GB)
While once essential, optical drives are now rare in laptops. They've been largely replaced by faster, higher-capacity USB drives and cloud storage.
🗣️ Discussion Time
- What are the three main advantages of an SSD over an HDD?
- Why would a user choose a computer with both an SSD and an HDD?
- What technologies have replaced optical drives for software installation and watching movies?
📝 Key Takeaways
- Secondary storage is non-volatile, providing long-term memory for your computer.
- HDDs are mechanical drives offering high capacity at a low cost, ideal for mass data storage.
- SSDs are flash-based drives that are much faster and more durable, perfect for operating systems and apps.
- Optical drives (CD, DVD, Blu-ray) are a slower, portable storage format that is becoming increasingly obsolete.
Thank You!
Any questions?