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.