Secondary Storage

Learning Objectives

  • Distinguish between primary and secondary storage.
  • Identify the characteristics of secondary storage:
    • Media
    • Capacity
    • Storage devices
    • Access speed
  • Describe components of hard disks:
    • Platters
    • Tracks
    • Sectors
    • Cylinders
    • Head crashes
  • Compare types of hard drives:
    • Internal
    • External
  • Analyze performance enhancements:
    • Disk caching
    • RAID
    • File compression and decompression
  • Define optical storage formats:
    • Compact discs (CD)
    • Digital versatile discs (DVD)
    • Blu-ray discs
  • Define solid-state storage types:
    • Solid-state drives (SSD)
    • Flash memory cards
    • USB drives
  • Define cloud storage and its services.
  • Describe mass storage devices and systems:
    • Mass storage
    • Enterprise storage systems
    • Storage area networks (SAN)

Introduction

  • Data storage has evolved beyond basic text and numeric files to accommodate much larger digital files (music, photos, video).
  • Understanding the different types of secondary storage is essential due to their varied capabilities and limitations.

Storage Types

Primary Storage

  • Volatile Storage: Content is lost when power is lost (e.g., RAM).
  • Temporary Storage: Used for active processing tasks.

Secondary Storage

  • Nonvolatile Storage: Retains data regardless of power (e.g., hard drives, SSDs).
  • Permanent Storage: Stores data for long-term use.

Characteristics of Secondary Storage

  • Media: Physical material that holds data (e.g., disks, tapes).
  • Capacity: How much data the storage medium can hold, typically measured in bytes (GB, TB).
  • Storage Devices: Hardware that accesses and manipulates data on the media (e.g., hard drives, SSDs).
  • Access Speed: Time required to retrieve or write data, measured in milliseconds.

Hard Disk Structure

  • Saves files by changing the magnetic charges on its surface to represent binary data (1s and 0s).
  • Consists of multiple platters arranged vertically, tracks (circular paths on platters), sectors (sections of tracks), and cylinders (vertical stack of tracks).
  • Head Crashes: An event where read/write heads touch the disk surface, potentially causing data loss.

Types of Hard Disks

  • Internal Hard Drives: Installed within the computer.
  • External Hard Drives: Connect via USB or other ports for added storage.
  • Network Drives: Accessible over a network for multiple users.

Performance Enhancement Techniques

  • Disk Caching: Anticipates data needs for faster access, by storing frequently accessed data in RAM.
  • RAID: Combines multiple disk drives for reliability and performance via redundancy.
  • File Compression: Reduces file size to save storage space.
  • File Decompression: Expands compressed files back to their original size.

Optical Disks

  • Utilize reflected light to read data with lands (representing 1s) and pits (representing 0s).
  • Organization on the disk involves using tracks and sectors, but unlike hard drives, optical disks typically utilize a single track.

Optical Disk Formats

  • CD: Capacity of 700 MB; standard for audio and data.
  • DVD: Capacity of 4.7 GB; used for video content.
  • Blu-ray: Up to 50 GB; used for high-definition videos.
  • UHD Blu-ray: 100 GB; intended for 4K video.

Types of Optical Disks

  • ROM: Read-only memory; cannot be written to.
  • R: Recordable; can be written to once.
  • RW or RAM: Rewritable; can be written to and erased multiple times.

Cloud Storage

  • Utilizes the internet to provide scalable storage solutions via servers.
  • Companies providing services include:
    • Dropbox
    • Google Drive
    • Microsoft OneDrive
    • Amazon Drive
    • Apple iCloud

Cloud Storage Benefits

  • Ease of uploading and sharing files.
  • Considerations:
    • What type of files to store.
    • Tools and hardware required.
    • Sharing methods.

Mass Storage Devices

  • Address the needs of large organizations for extensive secondary storage.
  • Types of devices include:
    • File servers
    • RAID systems
    • NAS (Network Attached Storage)
    • Cloud storage solutions.

Storage Area Network (SAN)

  • A specialized network providing access to consolidated, block-level data storage, allowing multiple servers to access storage over a network efficiently and securely.

Careers in IT

  • Disaster Recovery Specialists: Focus on data recovery post-disaster.
    • Education: Bachelor’s or associate’s degree in related fields.
    • Skills: Networking, security, and database management.
    • Salary: Ranges from $70,500 to $87,000 annually.

Future Storage Technologies

  • Potential advancements may involve storing digital data using heat, lasers, or DNA.
  • Innovations aim to increase storage capacity without expanding physical dimensions.