storage device resources

Storage Devices and Media Overview

• Types of Storage Devices:

  • Magnetic Devices

    • Hard Disk Drive (HDD)

    • Magnetic Tape Drive

  • Optical Devices

    • CD, DVD, Blu-ray read/write devices

  • Solid State Devices

    • Solid-State Drive (SSD)

    • Flash Drives (including USB drives and pen drives)

Secondary Storage

• Definition: Secondary storage includes non-volatile devices not part of primary memory (RAM and ROM), allowing data to be stored indefinitely.

• Characteristics:

  • Larger capacity than primary memory

  • Slower data access compared to primary memory

• Uses: All applications, operating systems, device drivers, documents, photos, and music are stored here.

Types of Secondary Storage by Media Type

• Magnetic Media

• Optical Media

• Solid-State Media

Key Terminology

• Storage Media: Hardware where data is physically stored (e.g., a CD or DVD)

• Storage Device: Hardware used to read/write to the media (e.g., a CD/DVD reader/writer)

3.1 Magnetic Media and Magnetic Storage Devices

• Principle: Based on magnetism; uses iron oxide to represent binary data (1s and 0s).

• Advantages:

  • Permanent data state unless overwritten

  • High data density allows large storage capacities

• Common Devices:

  • Magnetic Tape Drives

    • Uses: Best suited for batch processing and long-term archiving (e.g., bank cheques, utility billing).

    • Advantages: Cost-effective, robust, high capacity.

    • Disadvantages: Slow data access time, requires updating via master and transaction tapes.

  • Hard Disk Drives (HDD)

    • Data stored on rotating platters with magnetic surfaces.

      • Multiple platters in a drive, each with read/write heads.

    • Direct access: Can read specific data without sequentially reading prior data.

      • Actuator mechanism for moving read/write heads.

      • Data organized in tracks and sectors with a File Allocation Table.

    • Uses: Operating systems, applications, working data.

    • Advantages: Fast data transfer and access.

    • Disadvantages: Vulnerable to physical damage and mechanical failure; noisy operation.

3.2 Optical Media and Optical Storage Devices

• CDs and DVDs: Use laser technology for reading/writing data.

  • Formats: CD-R (write once), CD-RW (rewritable), DVD-ROM (read-only).

  • Structure: Data stored as pits on a spiral track.

• Blu-ray Discs: Superior storage capacity due to smaller physical features and blue laser technology.

  • Advantages: Large capacity and fast data transfer rates.

  • Applications: Movies, video games, data backup.

3.3 Solid-State Media and Solid-State Storage Devices

• Flash Storage: Uses NAND technology with no moving parts; faster access and lower power consumption.

  • SSDs: Provide faster data access than HDDs, suitable for modern portable devices.

    • Pros: Lightweight, faster speed, no moving parts.

    • Cons: Limited write endurance compared to HDDs.

• Memory Cards: Types include SD, XD, and CFast cards; used for cameras and portable devices.

  • Advantages: Compact and high-capacity.

  • Disadvantages: Smaller storage compared to HDDs and potential for loss.

3.4 The Future of Storage Devices

• Shift towards digital storage solutions (cloud, USB drives).

• CDs and DVDs declining in usage; streaming services gaining popularity.

Advantages of magnetic tapes

» They are generally less expensive (per byte) than the equivalent hard disk drive.

» It is a very robust technology (they do not deteriorate much over time and

remain stable).

» They have a huge data storage capacity.

» The data transfer rate is actually fast (this should not be confused with data

access time which is very slow for magnetic tapes).

Disadvantages of magnetic tape

» Very slow data access times (they use serial access,

which means all the previous data needs to be read until

the required data is found) - whilst magnetic tape data

access time is slow, the data transfer rate is still high.

» They are affected by magnetic fields