Storage Devices (Grade 11 NSC Matric Computer Application Technology): Revision Notes
Storage Devices
Introduction to storage
Computer storage has evolved tremendously since the early days of computing. To put this growth in perspective, consider that all the data required to send humans to the moon was approximately 600 MB - a relatively small amount by today's standards. Modern storage devices can hold thousands of times more data than those early computer systems.
Understanding storage capacity is essential when working with modern computing systems. The exponential growth in storage capabilities has enabled everything from high-definition video streaming to complex data analytics that would have been impossible just decades ago.
Remember that one gigabyte (GB) equals megabytes (MB), and one terabyte (TB) equals GB. These conversion factors are crucial for calculating storage requirements and comparing different storage options.
Worked Example: Storage Capacity Calculation
If you have a 2 TB external hard drive, how many GB of storage does this provide?
Step 1: Apply the conversion formula
Step 2: Calculate total capacity
Therefore, a 2 TB drive provides 2,048 GB of storage space.
Primary storage
Primary storage refers to the main or internal memory of a computer system. This type of storage is directly accessible by the CPU (Central Processing Unit) and serves as the location where essential instructions for the computer's operations are stored. The CPU can quickly access and execute these instructions as needed for the system to function properly.
The most common types of primary storage are RAM (Random Access Memory) and ROM (Read-Only Memory). The key characteristic of primary storage is that it holds data temporarily whilst the computer is running and receiving power. Think of primary storage as the computer's "working space" - similar to how you might use your desk to spread out papers you're currently working on.
Critical Concept: Volatile Memory
When the computer is switched off or loses power, the data stored in primary storage is cleared and lost. This temporary nature makes primary storage ideal for holding information that the computer needs immediate access to, but it's not suitable for permanent data storage.
Secondary storage
Secondary storage, also known as external, auxiliary, or secondary memory, serves a completely different purpose from primary storage. This type of storage is designed to hold data for extended periods, providing long-term storage solutions for your important information.
Unlike primary storage, data stored on secondary storage devices can only be removed by deliberately deleting it. This is where the computer permanently stores the operating system, hardware drivers, and all the data files created by users. The crucial advantage of secondary storage is that it preserves information even during power failures or when the computer is switched off.
Common examples of secondary storage include the hard drive inside your computer, solid-state drives (SSDs), USB flash drives, and secure digital (SD) cards. Each of these devices provides non-volatile storage, meaning your data remains safe regardless of the computer's power status.
Memory versus storage comparison
Understanding the fundamental differences between memory and storage is essential for computer literacy. Memory (such as RAM) requires continuous power to maintain its contents, making it volatile. This characteristic means that when you switch off your computer, anything stored only in memory will be lost permanently.
In contrast, storage devices maintain their contents even when the computer is switched off, making them non-volatile. Storage serves as the permanent home for your programmes and data, ensuring they remain available whenever you need them.
Performance vs Cost Trade-offs
From a performance perspective, memory provides much faster access speeds but comes at a higher cost per gigabyte compared to storage. Storage devices, particularly those with mechanical components like traditional hard drives, operate more slowly. Even electronic storage solutions like SSDs, whilst faster than mechanical storage, still operate at lower speeds than memory.
Storage media for backup
One of the most important uses of storage devices is creating backups or archives of your valuable data. In our digital world, there's a constant need to store information securely and permanently, ensuring it doesn't get accidentally destroyed, corrupted, or damaged.
Backups serve as safety copies of important information that you access regularly. These copies are typically kept for relatively short periods and updated frequently to reflect the current state of your data.
Types of backup devices
External hard drives (HDDs)
External hard drives offer fast performance and are generally reliable for backup purposes. However, because they contain mechanical moving parts, frequent use can create mechanical stress that may shorten their lifespan. Additionally, external hard drives can be fragile and susceptible to damage from drops or impacts.
External solid-state drives (SSDs)
SSDs provide an excellent backup solution because they contain no moving parts, making them more durable than traditional hard drives. The main drawbacks are their higher cost compared to HDDs and limited storage capacity due to the expense - the more storage space you need, the more expensive the SSD becomes.
USB flash drives
These devices are popular because they're inexpensive and relatively simple to use. USB flash drives have no moving parts, making them excellent for transporting data between locations. However, they can be slow to write data and may prove unreliable over time, especially with frequent use.
Tape backup systems
Tape backup involves copying data from a primary storage device to a tape cartridge, providing a way to recover information if there's a hard disc crash or failure. Tape backups can be performed manually or programmed to happen automatically using appropriate software.
CDs and DVDs
Although still occasionally used, optical discs like CDs and DVDs are much slower and less convenient than other modern backup methods. They also have significantly lower storage capacity compared to portable hard drives and most flash drives, making them less practical for backing up large amounts of data.
Online storage and backup services
Cloud-based storage services offer virtually unlimited storage space, meaning you can back up your entire hard drive, including all programmes, music, photos, and files. The advantage of cloud storage is that your data is saved to remote servers in different locations, providing protection even if your local computer is damaged or stolen.
Security Considerations for Cloud Storage
You must keep your login credentials secure, as compromised usernames and passwords could result in data loss or unauthorised access to your information.
Archiving versus backup
It's important to understand the distinction between backup and archiving. The data stored in a backup represents a copy of current and active operational information that a business or individual uses regularly. These files are currently being accessed and modified on a frequent basis.
Archiving, on the other hand, involves the long-term storage of information that will be used in the future but is not currently active. Archived data typically consists of original information that has been moved from its original location and is no longer being actively used or frequently accessed.
Several storage media options exist for archiving purposes. Magnetic tape offers very large storage capacity (up to 180 TB) but can be easily destroyed, potentially resulting in permanent data loss. Online storage services provided by companies like Amazon AWS offer relatively inexpensive packages specifically designed for long-term storage and archiving needs.
Key Points to Remember:
- Primary storage is volatile and directly accessed by the CPU, whilst secondary storage is non-volatile and provides permanent data storage
- Memory is faster but more expensive than storage, and it requires power to maintain data
- One gigabyte equals megabytes, and one terabyte equals gigabytes
- Different backup devices have varying advantages: SSDs are durable but expensive, HDDs are fast but fragile, and cloud storage offers unlimited space but requires secure credentials
- Backup involves copying current active data, whilst archiving involves long-term storage of inactive data